PERCENTAGES :-
By a certain percent, we mean that many hundredths. Thus x percent means x hundredths written as x%.
So x% = x/100.
EXAMPLE:
1. 20% = 20/100 = 1/5
2. 48% = 48/100 = 12/25
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*100)%=60%
If the price of commodity increases by r%,then the reduction in consumption so as not to increase the expenditure is given as follows
[r/(100+r)*100]%
If the price of commodity decreased by r%,then the increase in consumption so as not to decrease the expenditure is given as follows
[r/(100-r)*100]%
RESULT ON POPULATION:
Let the population of a town be P now and suppose it increases at the rate R% per annul then
i) Population after n years = P[1+(R/100)]n
ii) Population n years ago = P/[1+(R/100)]n
RESULT ON DEPRECIATION:
Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annul, then
i) Value of machine after n years = P[1-(R/100)]n
ii) Value of machine after n years = P/[1-(R/100)]n
IMPORTANT
i) If A is R% more than B,then B is less than A by [(R/(100+R))*100]%
ii) If A is R% less than B,then B is more than A by [(R/(100-R))*100]%
