Arithmetic Aptitude :: Percentage
Percentage - Important Formulas
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Concept of Percentage:
By a certain percent, we mean that many hundredths.
Thus, x percent means x hundredths, written as x%.
To express x% as a fraction: We have, x% = X100 . Thus, 20% = 20100= 15 . To express as a percent: We have, ab = 
ab x 100 
%.ab Thus, = 14 100 %= 25%. 14 -
Percentage Increase/Decrease:
If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is:
R(R∗100)x 100 
%If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:
x 100 %R(R−100) -
Results on Population:
Let the population of a town be P now and suppose it increases at the rate of R% per annum, then:
1. Population after n years = P 1 + R100 n 2. Population n years ago = 1 + R100 n -
Results on Depreciation:
Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annum. Then:
1. Value of the machine after n years = P 1- R100 n 2. Value of the machine n years ago = 1- R100 n 3. If A is R% more than B, then B is less than A by R100+Rx 100 %.4. If A is R% less than B, then B is more than A by R100−Rx 100 %.