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, ¼ =[(1/4)*100] = 25%;
0.6 =6/10 =3/5 =[(3/5)*100]% =60%
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
If A is R% less
than B , then B is more than A by
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