Question

two positive numbers x and y are inversely proportional.if x increased by 20%, then percentage decreases by

Answer 1

Let x and y be both 10, 
then xy = Constant
=> 10x10 = Constant

If x increases by 10%, then the new value of x will be 11. And the product of x and y will be 110. But product of x and y should be constant( 100 in this case.) Then y should be decrease to keep the product constant.Now,
xy = 100
11y = 100
y = 100/11
And in percentage terms

[(10 - 100/11)/ 10] x 100 = (10/110) x 100 = 100/11 %