How to calculate the percentage of the number? How to calculate interest?
I usually calculate the percentages as follows: I make up a proportion in my mind. For example, I need to find out how many percent 4 a person from 50 will be. I write in my mind 50 people - this is 100 percent. 4 rights - this is X percent. Then X = 100 * 4 / 50. As a result, we get 8 percent.
When in the mind you need to quickly calculate the percentage, usually it is required when calculating the discount in the store, and there% usually round (5, 10, 20%). I immediately estimate how much 10% will be (100 is 10, 200 is 20, that is, a tenth part), and based on the result, either divide it by 2 (get 5%) or multiply it by 2 (get 20%) .
For example: the price 173 ruble, discount 15%, how much is it?
from 173 - 17.3 is 10%
17.3 is divided into 2 is 8.65 - 5%
17.3 + 8.65 = 25.95 (10% + 5%)
Total we get 173-25.95 = 147.05
In fact, you can not count pennies, about you will still know how much this is.
I do not have much mathematics at all.)) But I always make up the proportion in my mind and thus calculate the percentage. For example, you want to know 20 percent per annum of the amount. And the amount, for example 20 thousand. I form the proportion:
20 thousand - 100 percent
x thousand - 20 percent.
x = 20 thousands multiply 20 percent, and then divide by 100.
You get 400.)))
1) Multiply the number by 0, the desired percentage. for example: 27%, this number is * 0,27%
2) the number is divided by 100, then multiplied by the desired percentage-x / 100 * 27, we find 27% of X
3) If you want to find an even number%: 50% - divide the number by 2, 25% - divide by 4, 20% 5, 10% 10. 5% -20,2005- multiply by 2. The principle is probably understandable
Calculate the percentage
1 percent is the 1 hundredth part of the number. Therefore, in order to calculate the percentage some number, you must multiply this number by the specified number of percentages, and divide the result into 100.
And here, by the way, the online interest calculator.
As we all know, even from school, the percentage is the hundredth part of something expressed in numbers. That is, in order to calculate the interest, you need to divide the figure into 100. For example, you need to determine the percentage of the 278 digit. Divide by one hundred and get - 2,78%.
The easiest way to calculate the correct percentage from a number is to first find out what 1% will be.
To calculate 1%, you need to divide the existing number into 100.
Having got the number of what is equal to 1%, it is not difficult to calculate how much will be, for example, 18% - you need to multiply the resulting number by 18.
There is a number of 98, you need to calculate 18% of this number.
98 divide by 100 = 0,98 is 1%
And now 0,98 is multiplied by 18
0,98 x 18 = 17,64.
The second way is slightly more difficult - you need to make a proportion.
98 - 100%
X - 18%
The proportion is calculated as follows:
98 x 18 / 100 = 17,64
That's how I usually calculate interest.
Very often the calculation of interest is used in practice in trade. On a simple example I'll show you two options:
the store received the goods at a cost of 100 rubles and made an 20% surcharge
1) 100p + 100p / 100% * 20% = 120 rubles the price of the product after the allowance (here 20 rubles is 20%)
2) 20p: 120р / 100% = 16,67% (here 20 rubles is 16,67%).
This means that if you make a markup of 20%, you will get 16,67% of the profit from the tree as a result.
Interest from the number is easy to calculate. You need to divide the number by 100 and multiply by the percentage you need to get. For example, we need to calculate 20% of 5 kilograms of apples. We divide 5 kg by 100 and multiply by 20% = 1 kg of apples.
The number is multiplied by 100 and divided by the percentage you want to calculate.
Or vice versa .. divide the number by 100 (get 1 percent), now the number is multiplied by the number of percent. that's all, for example, if the whole number is 400, you need to calculate 12 percent, then 400: 100 = 4 (1 percent). 4 * 12 = 48 (12%)