Interest calculation is easy mathematical operation, which is quite common in Everyday life. For example, you need to calculate how much a person saves by using a store's discount card or buying a product at a sale at a discount, at what percentage he takes a loan. Interest can be calculated using a calculator or proportion, a formula for calculating percentages and knowledge of elementary known ratios will come in handy.
What is a percentage of a number
The calculation of interest in the school curriculum is studied in the 5th grade, if not earlier. By definition, a percentage is one hundredth of a number. The term appeared in Ancient Rome and literally translates as "from a hundred." Initially, the idea of calculating percentages originated in Babylon. Parallel to ancient india Learn how to calculate percentages using proportions.
To find the percentage of a number, you need given number divide by 100. Obviously, 1% of 100 equals one.
Calculating interest using formulas
The formula for finding the percentage of a number is elementary. It is necessary to divide the number by 100, and then multiply by the desired percentage.
If we take the original number as X, and the desired percentage as Y, then the formula is written as X/100*Y=...
Calculations using proportion
Percentages can be calculated with an understanding of the proportion method. Let A be the main number taken as 100%, B be the number whose ratio with A in percentage must be calculated, and X is the number of desired percentages. Then:
A - 100%,
B - X%.
Multiplication crosswise will give equality: A * X \u003d B * 100. Therefore, X=B*100/A.
For example, you need to find out how many percent of 300 is the number 75. It turns out: 75*100/300=25%.
Alternative Calculation Method
Let's imagine one percent not as a decimal, but as a simple fraction - 1/100. Similarly, you can write any number of percentages. So, 10% is 0.1 or 1/10, 25% is 0.25 or 25/100=1/4 and so on. Therefore, finding 10% of the number is quite simple - you need to divide the original number by 10. In this way it is convenient to calculate 20, 25 and 50 percent:
- 20% is 1/5, so you need to divide the original number by 5.
- 25% - 1/4, must be divided by 4.
- 50% is 1/2, just divide by two.
But not every percentage is convenient to calculate in this way. For example, 33% is 33/100, which when written as a decimal gives 0.3333 with an infinite number of triplets after the decimal point.
If you have doubts about the correctness of the calculations, you can always check yourself on the calculator, which is now available in any mobile device and on any computer.
Interest in modern world spinning all over the place. Not a day goes by without using them. When buying products, we pay VAT. When we take a loan from a bank, we pay the amount with interest. When reconciling income, we also use percentages.
Working with percentages in Excel
Before starting work in Microsoft Excel remember school lessons mathematics, where you studied fractions and percentages.
When working with percentages, remember that one percent is a hundredth (1%=0.01).
Performing the action of adding percentages (for example, 40 + 10%), first we find 10% of 40, and only then we add the base (40).
When working with fractions, do not forget about the elementary rules of mathematics:
- Multiplying by 0.5 is equal to dividing by 2.
- Any percentage is expressed as a fraction (25%=1/4; 50%=1/2, etc.).
We count the percentage of the number
To find the percentage of a whole number, divide the required fraction by the whole number and multiply the result by 100.
Example #1. There are 45 items in stock. 9 units sold per day. How much of the product was sold as a percentage?
9 is a part, 45 is a whole. We substitute the data in the formula:
(9/45)*100=20%
We do the following in the program:
How did it happen? Having set the percentage type of calculations, the program will independently add the formula for you and put the “%” sign. If we set the formula on our own (with multiplication by one hundred), then there would be no “%” sign!
Example #2. Let's solve the inverse problem. It is known that there are 45 units of goods in the warehouse. It also states that only 20% have been sold. How many units were sold in total?
Example #3. Let's try the acquired knowledge in practice. We know the price for the goods (see the picture below) and VAT (18%). You need to find the amount of VAT.
We multiply the price of the goods by the percentage, according to the formula B1 * 18%. 
Advice! Do not forget to extend this formula to the rest of the lines. To do this, grab the lower right corner of the cell and lower it to the end. Thus, we get the answer to several elementary problems at once.
Example number 4. Reverse problem. We know the amount of VAT for the goods and the rate (18%). You need to find the price of the item.
Adding and subtracting
Let's start by adding. Let's consider the problem on a simple example:
Now let's try to subtract the percentage from the number. With the knowledge of addition, subtraction will not be difficult. Everything will work by replacing one "+" sign with a "-". The working formula will look like this: B1-B1 * 18% or B1-B1 * 0.18. 
Now let's find percentage of all sales. To do this, we sum up the quantity of goods sold and use the formula B2/$B$7.
Here are such elementary tasks turned out. Everything seems simple, but many people make mistakes when doing this.
Making a chart with percentages
There are several types of charts. Let's consider them separately.
Pie chart
Let's try to create a pie chart. It will display the percentage of the sale of goods. To begin with, we are looking for percentages of all sales.
After, your chart will appear in the table. If you are not satisfied with its location, then move it by dragging outside the diagram. 
bar chart
For this we need data. For example, sales data. To create a histogram, we need to select all the numeric values (except for the total) and select the histogram in the "Insert" tab. To create a histogram, we need to select all the numeric values (except for the total) and select the histogram in the "Insert" tab. 
Schedule
You can use a graph instead of a histogram. For example, a histogram is not suitable for tracking profits. It would be more appropriate to use a graph. The graph is inserted in the same way as the histogram. You need to select a chart in the "Insert" tab. One more chart can be superimposed on this chart. For example, a chart with losses. 
This is where we end. Now you know how to rationally use percentages, build charts and graphs in Microsoft Excel. If you have a question that the article did not answer, write to us. We will try to help you.
In the process of solving various kinds of tasks, both educational and practical, users often turn to Excel.
Spreadsheets allow you to analyze data, build charts and graphs, and perform a variety of calculations. One common operation is the calculation of percentages. Ability to competently produce necessary calculations- a useful skill that finds successful application in almost all areas of life. What techniques will help you calculate percentages using Excel spreadsheets?
How to calculate percentages in Excel - the basic calculation formula
Before proceeding with the calculation of percentages, it is necessary to define the terminology. The term "percentage" means the number of shares out of all 100 shares of the whole. The mathematical definition of a percentage is a fraction, the numerator of which determines the desired number of parts, and the denominator is the total. The result is multiplied by 100 (because the integer is 100%). Working with a spreadsheet, the formula for determining the percentage is as follows:
Part/Whole = Percentage
It differs from the usual interpretation in mathematics only by the absence of further multiplication by 100. The properties of the table fields will help you get the necessary value format - just activate the Percent cell format.
Example 1
Here is a series of data entered, for example, in column D (D2, D3, D4, D5, ...). It is necessary to calculate, 5% of each value.
- Activate the cell next to the first value (or any other) - it will contain the result of the calculations.
- In cell E2, write the expression "=D2/100*5" or "=D2*5%".
- Press Enter.
- "Drag" cell E2 to the required number of lines. Thanks to the autocomplete token, the above formula will also calculate the rest of the values.
Example 2
You have 2 columns of values in front of you - for example, sold cakes (D2, D3, D4, D5, ...) and the total number of baked goods (E2, E3, E4, E5, ...) of each type. It is necessary to determine what part of the product is sold.
- In the cell where the result will be calculated (for example, F), write the expression "=D2/E2".
- Press Enter and "stretch" the cell for the required number of lines. Using the autofill marker will allow you to apply this formula to all subsequent cells and make the correct calculations.
- To convert the result to percentage format, select the required cells and use the Percent Style command. To activate the latter, you can right-click and select the "Format cells" - "Percentage" item in the list that appears. In doing so, you specify the desired number of decimal places. Or go to the "Home" - "Number" section and select the "Percentage" view.
How to calculate percentages in Excel - percentage of the amount
To calculate the proportion of each part relative to the total, use the expression "=A2/$A$10", where A2 is the value of interest, the total is indicated in cell A10. What if the position you are interested in appears in the table several times? In this case, use the SUMIF (SUMIF) function with the following parameters:
SUMIF(range,criteria,sum_range)/total
SUMIF(range, criterion, sum_range)/total sum
- Move to the cell where the result will be obtained.
- Write the expression "=SUMIF(C2:C10;F1;D2:D10)/$D$14" (or =SUMIF (C2:C10;F1;D2:D10)/$D$14), where
C2:C10, D2:D10 - ranges of values within which calculations occur,
F1 - a cell in which the studied characteristic is indicated,
D14 is the cell in which the amount is calculated. 
How to Calculate Percentages in Excel - Percent Change
The need for such calculations often arises in the course of assessing the increase or decrease in performance. So, sales volumes by product categories for 2015. entered in column D, similar data for 2016. - in column E. It is necessary to determine by what percentage the volume of sales increased or decreased.
- In cell F2, enter the formula "=(E2-D2)/D2".
- Convert cell data to Percentage format.
- To calculate gain or loss for other categories (cells), drag F2 to required amount lines.
- Evaluate the result. If the value is positive, you have an increase; if negative, you have a decrease.
How Interest Works
.
interest is one of mathematical concepts which are often encountered in everyday life. You can read or hear, for example, that 57% of voters took part in the elections, the rating of the winner of the hit parade is 75%, academic performance in the class is 85%, the bank charges 17% per annum, milk contains 1.5% fat, the material contains 100% cotton, etc.
It is clear that without understanding this kind of information in modern society it would just be difficult to exist.
I conducted a survey among people aged 7 years and older, finding out their understanding of what PERCENT is and how it works.
A percentage is a hundredth of a number - 80%
It follows from this that most of the population knows what interest is, but not everyone understands how it works.
Percentage is something from mathematics -15%
Interest is profit - 3%
Difficult to answer - 2%History of interest creation.
The word "percentage" itself comes from the Latin. "pro centum", which means "hundredth part" in translation. In 1685, the book Manual of Commercial Arithmetic by Mathieu de la Porte was published in Paris. In one place, it was about percentages, which then meant "cto" (short for cento). However, the typesetter mistook that "cto" for a fraction and typed "%". So because of a typo, this sign came into use.
Interests were also known in India. Indian mathematicians calculated percentages using the so-called triple rule, that is, using a proportion.
were widespread in ancient Rome cash settlements with interest. The Roman Senate set the maximum available interest charged from the debtor.
In Europe, trade expanded during the Middle Ages and, consequently, Special attention applied to the ability to calculate percentages. Then it was necessary to calculate not only interest, but also interest on interest (compound interest). Often, offices and enterprises developed special interest calculation tables to facilitate calculations. These tables were kept secret, they were a trade secret of the company. The tables were first published in 1584 by Simon Stevin.
The Flemish scientist, military engineer Simon Stevin was not a mathematician by profession, but his diligence and talent allowed him to take his rightful place among the outstanding European mathematicians. He was the first in Europe to discover decimals. Simon Stevin published a table for calculating compound interest, which was used in trade and financial transactions.
AT practical life it is useful to know the relationship between the simplest percentages and the corresponding fractions: half - 50%, a quarter - 25%, three quarters - 75%, a fifth - 20%, three fifths - 60%, etc.
To increase by 2 times means to increase by 100%, to decrease by 2 times means to decrease by 50%. Modern life again makes interest tasks relevant, as the scope of practical application of interest calculations is expanding. Everywhere - in newspapers, on radio and television, in transport and at work, the increase in prices, wages, the growth in the value of shares, the decrease in the purchasing power of the population, etc. are discussed. Let's add here the announcements of commercial banks attracting money from the population for various conditions, information on income from shares of various enterprises and funds, on changes in the percentage of bank loans, etc. All this requires the ability to make at least simple percentage calculations for comparison and selection of more favorable conditions. The formation of relevant skills currently leaves much to be desired.
Of particular interest to me is interest in banking transactions.
So, if when calculating any data, percentages simplify mathematical calculations, then there is a need to study them.
Purpose of work: study practical application interest calculations.
The simplest problems with percentages.Tasks:
- Define the concept of "percentage";
- To study the history of the origin of interest;
- Determine the scope of practical application of interest;
- Solve the simplest tasks for interest and tasks for banking operations;
- Make a conclusion.
Object of study: percentage.
Subject of study: tasks for calculating interest in banking operations.
1. Finding a percentage of a number.
To find a percentage of a number, you need to multiply that number by the corresponding fraction.
For example.
20% of 45 kg of wheat is equal to 45*0.2=9 kg.2. Finding a number by percentage.
To find a number by its percentage, you need to divide the part corresponding to this percentage by a fraction.
For example.
If 8% of the length of the bar is 2.4 cm, then the length of the entire bar is 2.4:0.08=30 cm.3. Finding the percentage of two numbers.
To find out how many percent one number is of the second, you need to divide the first number by the second and multiply the result by 100%.
For example.
9 g of salt in a solution weighing 180 g is 9:180 * 100% = 5%.Bank interest.
Now consider the problem of calculating interest in banking operations.
There are many types of banking transactions. For example: lending individuals, lending legal entities, deposit, etc.
Let's show the formulas and examples of their use.
How to calculate interest on deposits?
In order to competently manage your funds placed in bank deposits, it is necessary to analyze the expected return on the selected types of deposits, making up the calculation of interest on deposits for this.
To do this, you need to know: the amount of the interest rate, the procedure and cyclicality of interest accrual, the procedure for receiving interest (addition to the deposit, cash withdrawal, transfer to a demand account or card). All this is stipulated by banks in bank deposit agreements and depends on the type of deposit.To calculate interest on deposits of individuals, banks use the following types of interest rates:
Calculation of interest on attracted funds (deposits) is carried out using standard formulas. The following interest formulas apply:
- A fixed rate is when the bank's interest rate is fixed in the deposit agreement and does not change during the entire term of the deposit under the agreement.
- A floating rate is when the interest rate originally set under the agreement may change during the entire term of the deposit, due to changes in the refinancing rate, changes in the exchange rate and other factors specified by the bank in the agreement.
1) The formula for calculating simple interest.
If the interest accrued on the deposit is added to the deposit at the end of the deposit term or not added at all, but transferred to a separate account, then in these cases the amount of interest is calculated using the simple interest formula. Simple interest does not involve interest capitalization. When choosing the type of deposit, you should pay attention to this. When the amount of the deposit is large, and the formula for calculating simple interest is used, then you can lose a significant amount of income. The formula for simple interest on deposits looks like this:
Sp = : 100, where
Sp - the amount of interest (income).S = P + : 100, where
S - the amount of the bank deposit (deposit) with interest;
I - annual interest rate;
t - the number of days of accrual of interest on attracted deposits;
K - number of days in a calendar year (365 or 366);
P - the amount of funds attracted to the deposit.For better understanding, I will conditional examples calculation of simple interest and the amount of a bank deposit with simple interest.
Example. Suppose that the bank has accepted a deposit in the amount of 50,000 rubles for a period of 3 months at a rate of 10.5 percent "annual".
Sp = 50,000 * 10.5 * 90: 365: 100 = 1294.52
S = 50,000 + 50,000 * 10.5 * 30:365:100 = 51,294.52
2) The formula for calculating compound interest.
If the interest accrued on the deposit is added to the deposit at regular intervals (daily, monthly, quarterly), then in these cases the amount of interest is calculated using the compound interest formula. Compound interest involves the capitalization of interest (the calculation of interest on interest). To calculate compound interest, you can use two formulas for compound interest on deposits, which look like this:
Sp = P*[(1 + I * t: K:100) n - 1] or
Sp = S - P = P * (1 + I * t: K: 100) n - P, where
I - annual interest rate;
t - the number of days of accrual of interest on attracted deposits;
K - number of days in a calendar year (365 or 366);
P - the amount of funds attracted to the deposit;
Sp - the amount of interest (income);
n is the number of interest accrual periods;
S - the amount of the deposit (deposit) with interest.However, when calculating interest, it is easier to first calculate the total amount of the deposit with interest, and only then calculate the amount of interest (income). The formula for calculating a deposit with interest will look like this:
S = P * (1 + I * t: K: 100) n
I will give conditional examples of calculating compound interest and the amount of a bank deposit with compound interest.
Example. A deposit was accepted in the amount of 50,000 rubles for a period of 90 days at a rate of 10.5 percent per annum with interest accrued every 30 days.
S = 50,000 * (1 + 10.5 * 30: 365:100)3 = 51,305.72
The correctness of the calculation of interest according to the example above can be double-checked. To do this, we divide the deposit term into 3 periods (month) and calculate the interest for each period. I use the simple interest formula.Sp = 50,000 * [(1 + 10.5 * 30: 365: 100)3 -1] = 1,305.72
1 month S1 = 50,000+50,000*10.5*30:365:100 = 50431.51
Sp1 = 50,000*10.5*30:365:100 = 431.51
Month 2 S2 = 50,431.51+50,431.51*10.5*30:365:100 = 50,866.74
Sp2 = 50431.51*10.5*30:365:100 = 435.23
3 month S3 = 50866.74+50866.74*10.5*30:365:100 = 51305.72
Sp3 = 50866.74 * 10.5*30:365:100 = 438.98
So, the total amount of interest, taking into account the monthly capitalization (calculation of interest on interest), is:
Sp = Sp1+Sp2+Sp3 = 1305.72, which corresponds to the amount calculated using compound interest. Thus, the calculation according to the calculation according to the compound interest formula is compiled and calculated correctly.
And now let's do a simple comparison of the results of calculating the interest, using two various formulas. In both examples, the same data were taken as the basis, i.e. savings in the amount of 50,000.00 rubles are placed in a deposit with a term of 90 days.
When calculating interest using the simple interest formula, the income amounted to 1294.52 rubles. When calculating interest using the compound interest formula, the income amounted to 1305.72 rubles. Interest capitalization amounted to 11.2 rubles. (1305.72 - 1294.52).
Conclusions.
- More income is obtained with the capitalization of interest, in this case, the compound interest formula is used in the calculation. I draw your attention to the fact that in the examples given, for convenience, only a fixed rate was used.
- These formulas can be used to calculate interest on loans.
Bibliography.
- Brue L.P. Money, banks, credit functions M. VSH 1993
- Banking. Reference manual. Ed. Yu. A. Babicheva. - M.: economics, 1994
- Material from Wikipedia - the free encyclopedia www.wikipedia.ru
- A.V. Shevkin "Solving text problems" Moscow " Russian word» 2002
Sometimes calculating percentages can be difficult, because it is not always easy to remember what we were taught in school. Let Excel do the work for you - simple formulas can help you find, for example, the percentage of the final value or the difference between two numbers as a percentage.
Important: The calculated results of formulas and some Excel worksheet functions may be slightly different between Windows x86 or x86-64 computers and Windows RT ARM computers.
Let's say your company sold $125,000 worth of goods this quarter and you need to calculate what percentage of $20,000 is of the total.
In 2011, the company sold goods in the amount of 485,000 rubles, and in 2012 - in the amount of 598,634 rubles. What is the difference between these percentages?
see also
Calculating the Percentage of the Total Value
Let's say that you answered 42 questions out of 50 correctly on the test. What is the percentage of correct answers?
Calculating the difference between two numbers as a percentage
Let's assume that your wage amounted to 23,420 rubles in November and 25,000 rubles in December. By what percent did your salary change in December compared to November? Then, if in January you earned 24,250 rubles, then by how many percent does this differ from December? You can calculate the difference by subtracting the new salary from the previous salary and then dividing the result by the sum of the previous salary.
Magnification Percentage Calculation
Reduction Percentage Calculation
Finding the Total Value with a Known Count and Percentage
Assume that the selling price of a shirt is $15, which is 25% below the original price. What is the initial price? AT this example find a number whose 75% is 15.
Finding the sum when you know the total and the percentage
If you purchase a computer for $800, you must pay an additional 8.9% sales tax. How much will this tax be? In this example, you need to find 8.9% of 800.
Increase or decrease a number by a given percentage
We spend an average of $113 per week on food, and we need to reduce this cost by 25%. How much can you spend on a weekly basis? Alternatively, there is an option to increase the $113 weekly limit by 25%. How much will the food cost per week be in this case?