ThePrismSolutions

ThePrismSolutions

PERCENTAGE

IMPORTANT FACTS AND FORMULAE

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, ΒΌ =[(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 as not 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 nyears = 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]%.



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