Question

A man spends 80% of his earnings his earnings increased by 25% and his expenses increased by 20% by what percent his savings increase

Answer 1

Let his earnings or income be I
Let his expenditure be E
and his savings be S

So, we have
I = E + S
Let income I be 100, so
then E = 80% of I and rest 20% will be S
so, E = 80, and S = 20
Now, his income increases by 25%, so 
I(new) = I + 0.25I = 1.25I = 125
and Expenditure also increases by 20%, so
E(new) = E + 0.2E = 1.2E = 1.2 * 80 = 96
So, we put values
I(new) = E(new) + S(new)
125 = 96 + S(new)
S(new) = 29
Increase in S will be = S(new) - S = 29 - 20 = 9
Percentage increase in S = 9/20 * 100 = 45%