How to solve problems with interest

The question often tormented in mathematics is: "Why do I need this?" may find the answer when the boss promises that next month wages will increase by 15%. Today, the ability to solve problems at interest is a vital necessity.

You will need

1) Paper 2) Pen 3) Calculator

Instruction manual

one

According to the vocabulary of Ozhegov Sergey Ivanovich, the percent is called the hundredth share (part) of the whole and is denoted by the sign%. The hundredth part can be written like this:

1% = 1/100 = 0.01

In the role of the whole, i.e. 100%, anything can appear: any number, a bunch of grapes, a keg of honey or a pension.

2

Examples

1) Find 18% of the pension equal to 6 122 p.

6 122 p. * 18% = 6 122 p. * 18/100 = 6 122 p. * 0.18 = 1101.96 p.

2) Pour a barrel of honey into 8 cans. Give 3 cans to guests. How many percent of the honey from the barrel did you give away? How much do you have left?

3/8 or 0, 375 of the barrel you gave away. Convert to percent, multiplying by 100. You gave 37.5% of the honey that you had. It remains 5/8 = 0.625 * 100% = 62.5%.

3

All interest tasks are easy to solve with proportion.

Find 82% of the number 506.

Proportion:

506 - 100%

X is 82%, where X is the unknown to be found.

506 / X = 100% / 82%, or immediately 506 * 82% = X * 100%

X = 506 * 82% / 100% = 414.92

Percentage (%) as a unit of measurement declined.

4

From a mathematical point of view, there are three main types of tasks for interest. The remaining tasks are formed on the basis of these types. Learn how to solve these problems.

5

First type

Find the percentage of the given number.

The average salary in your organization is 20 thousand rubles. Next year they promise to increase it by 20%. How much will the expected salary increase next year?

20 thousand p. - one hundred%

X - 20%

X = 20 thousand p. * 20% / 100% = 4 thousand p.

The expected average salary will increase by 4 thousand rubles. and amount to 24 thousand p.

6

Second type

Find the number by percentage.

40% of the tomato in the box, which amounted to 5 kg, turned out to be green. How much is a kilogram of tomato in a box?

5 kg - 40%

X kg - 100%

X = 5kg * 100% / 40% = 12.5 kg

7

Third type

Find the percentage of one number through another.

In the morning, Peter usually drinks 1 cup of tea, and in the evening - 4. How many percent of the evening volume of cups of tea he drinks in the morning?

4 cups - 100%

1 cup - X%

X = 1 cup * 100% / 4 cups = 25%

note

1) Carefully select the value that you designate as 100%. 2) If for 100% you indicated, for example, the number 200, then 99% - there will always be a number less than 200, and 101% - more. 3) After you have solved the problem, always analyze the answer - this will help to avoid mistakes.

Useful advice

Write down the conditions on paper - so the task will become clearer and clearer.

• http://mrcpk.marsu.ru/works_iso/2006-09-18/korotkovani/tip_zadach.htm
• Percentage and Relationship Tasks