Percentage - Aptitude Concepts (Important Facts And Formulae)

By Team tt24 - Wednesday, March 12, 2014 -

IMPORTANT FACTS AND FORMULAE

1. Concept of Percentage : By a certain percent ,we mean that many hundredths. Thus the x percent means x hundredths and can be 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,

¼ =[(1/4)*100] = 25%;

0.6 =6/10 =3/5 =[(3/5)*100]% =60%.

2. If the price of a particular commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is

[R/(100+R))*100]%.

If the price of a particular 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 city be P now, and suppose it increases at the rate of R% per annum. Then :

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

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

4. Results on Depreciation : Let the present value of a particular machine be P. Let it depreciates at the rate R% per annum. Then,

I. Value of the machine after n years = P[1-(R/100)]n.

II. 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]%.