NCHMCT JEE 2021 Question Paper with solutions for online practice

(a) Let, income of a person $=\mathit{₹}100$
$\because$ Spend on different expenses $=\mathit{₹}60$
$\therefore$ Total saving $=100-60=\mathit{₹}40$
Now, income after increment of $20\%$
$=\frac{120}{100}\times 100=\mathit{₹}120$
and expences after increment of $10\%$
$=120\times \left(60+10\right)\%$
$=120\times \frac{70}{100}=\mathit{₹}84$
$\therefore$ New saving $=120-84=\mathit{₹}36$
Now, percentage decrease $=\left(\frac{40-36}{40}\right)\times 100$

$=\frac{4}{40}\times 100=\frac{100}{10}=10\%$