SOLUTION —
Let the income of Devdatta
= Rs. 100 .
His expenditure $=75 \%$ of 100
$=$ Rs. 75
$\therefore$ His savings $=$ Rs. $(100-75)$
$=$ Rs. 25
Now his new income
$=100+20 \%$ of 100
$=100+20=$ Rs. 120
his new expenditure
$=$ Rs. $75+10 \%$ of 75
$=$ Rs. $75+7.50$
$=$ Rs. $82 \cdot 50$
So, New savings
$=$ Rs. 120 - Rs. $82 \cdot 50$
$=$ Rs. $37.50$
- So, his increase in savings
$\begin{array}{l}=\frac{\text { Rs. } 37.50-\text { Rs. } 25}{\text { Rs. } 25} \times 100 \\=50 \% \text {; Ans. }\end{array}$