Question

Given that A=xy find the percentage increase in A when both X and Y increase by 10%

Answer 1

A=xy
If there is 10% increase in x then,
New value of x = x + 10%of x =1.1x
similarly for y
New value of y after increase= 1.1 y
New value of A after increase in x and y = 1 .1x × 1.1 y= 1.21xy
now
increase amount in A= New value of A - old value of A
=1.21xy - xy= 0.21xy
percentage increase in A= (0.21xy÷xy )× 100= 21%