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# B is what percentage of A

## ФFormula for calculating what percentage of the number B from the number A.

If you know two number A and B and need find, B is what percentage of A, then

 P = B · 100% A

For the derivation of this equation using the method of solving problems with percentage

 "All" = 100% => "Part in %" = "Part" · "100%" "Part" "Part in %" All

## Examples of solving problems: B is what percentage of A

Example 1.
5 is what percentage of 40.

Solution.

 5 · 100% = 12.5% 40

Answer: 5 is 12.5% of 40.

Example 2.
In store book costs \$ 400 and \$ 380 on the market. Find what percentage of the market price in relation to the store?

Solution.

 380 · 100% = 95% 400

Example 3.
The bank deposit put \$ 10,000 in a year have profited of \$ 1200, what the interest rate was in the bank.

Solution. The interest rate is equal to a percentage, which is the profit of the deposit amount

 1200 · 100% = 12% 10 000

Answer: the interest rate was 12%.