Percentages Formulas - Aptitude Questions And Answers

#### Percentages Formulas - Aptitude Questions And Answers

• Posted by  Rajni
28 Jan, 2012

1.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% = x/100.

Thus, 20% =20/100 =1/5; 48% =48/100 =12/25, etc.

To express a/b as a percent : We have, a/b =((a/b)*100)%.

Thus, 1/4 =[(1/4)*100] = 25%; 0.6 =6/10 =3/5 =[(3/5)*100]% =60%.

2. If the price of a commodity increases by R%, then the reduction in consumption so asnot to increase the expenditure is
[R/(100+R))*100]%.
If the price of the commodity decreases by R%,then the increase in consumption so as to decrease the expenditure is
[(R/(100-R)*100]%.

3.Results on Population : Let the population of the town be P now and suppose it increases at the rate of
R% per annum, then :

1.Population after nyeras = P [1+(R/100)]^n.
2.Population n years ago = P /[1+(R/100)]^n.

4.Results on Depreciation : Let the present value of a machine be P. Suppose it depreciates at the rate
R% per annum. Then,
1.Value of the machine after n years = P[1-(R/100)]n.
2.Value of the machine n years ago = P/[1-(R/100)]n.

5.If A is R% more than B, then B is less than A by
[(R/(100+R))*100]%.
If A is R% less than B , then B is more than A by
[(R/(100-R))*100]%.