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Formulae and Questions of Percentage
1. Concept of percentage or Percentage formula
To express x% as a fraction: We have, x% x/100
Thus, 30%=30/100= 3/10
In simple terms we can conclude that percentage
symbol "%" means 1/100
In case we are having a fraction and we have to
calculate its percentage then we will multiply it by
100.
that is,
a/b=(a/b)×100)%
2. Increase or decrease in percentage with price
(1 ) If the price of a commodity increases by R%,
then the reduction in consumption so as not to
increase the expenditure will be = [R/ (100+R)×100]%
( 2 ) If the price of a commodity decreases by R%,
then the increase in consumption so as not to
decrease the expenditure will be = [R/(100−R)×100]
3. Results on population
Formula's on result of population are very important
when we have to calculate the population n years
after or n years before,
Let the population of a town be P now and suppose
it increases at the rate of R% per annum, then
(1 ) Population after n years =P(1+R/100) n
(2 ) Population before n years =P/(1+R/100 )n
4. Results on Depreciation
We know that value of a machine depreciate with
time, so it will decrease with the time. To calculate
the value of machine after n years or before n years,
we use these formula's
Let the present value of a machine be P. Suppose it
depreciates at the rate of R% per annum. (1 )
Population after n years = P(1−R/100) n
(2 ) Population before n years =P/(1−R/100) n
5. Important results for Percentage
The formulas we are going to mention below is same
as of increase or decrease in consumption with
increase or decrease in the commodity price, just
here we are in a bit different context.
(1 ) If A is R% more than B, then B is less than A by =
[R/(100+R)×100]%
(2 ) If A is R% less than B, then B is more than A by =
[R/(100−R)×100]%.