UPSC CDS 1 2018 Math Paper

Let the man reduce his consumption by x% to keep his budget same, then
100

+25%

––––––––>

125

––––––––>

−x%

100
⇒x=

25

125

×100%
=20%
Formula: If the price of wheat rises by r%, then the reduction in consumption in order to keep his budget same as before
=(

r

100+r

)×100%
=(

25

100+25

)×100%=20%