Some Important Tricks for Percentage

• TRICK(1): y%  of x = xy / 100. Example: 20% of 50 = ?

soln: 50 X 20/100 = 10

• TRICK(2): Represent y in the form of percentage of x is x/y X 100. Example: What percentage of 20 is 30? soln: 30/20 X 100 = 150%.

• TRICK(3): If A is x% more than B, then B is how much percentage less than A, (x/100-x) X 100%.

Example: If the amount of A is 25% more than the amount of B then the amount of B is how much less than the amount of A?
Soln: (25/ 100 +25) X 100 = 100/5 = 20%.

• TRICK(4): If A is x% less than B , then how much more is B than A?

 Example: If the amount of Ram is 20% less than Shyam then how much more amount of Shyam than the amount of Ram? Soln: (20/100-20) X 100 20/80= 25% more.

• TRICK(5): If the price of a commodity increases by x%, then reduction in consumption as not to increase the expenditure is [x/(100+x) X 100 ].

I the price of a commodity decreases by x%, then the increase in consumption as not to decrease the expenditure is [x/(100-x ) X 100 ].

• TRICK(6): Let the population of a town be P now and suppose increases at the rate of x% per annum, then population after n years = P(1 + x/100)^n  And population  n years ago = P/(1 + x/100)^n.