Question

A number is increased by $10\%$ and then it is decreased by $10\%$. Find the net increase or decrease percent. [3 MARKS]

Answer 1

Concept : 1 Mark
Calculation : 2 Marks

Let the number be 100

Increase in the number $=10\%=10\%of100=10$

$\therefore$ Increased number = 100 + 10 = 110

This number is decreased by $10\%$

$\therefore$ Decrease in the number
$=10\%=10\%of110=(\frac{10}{100}\times 100)=11$

$\therefore$ New number = 110 - 11 = 99

Thus, net decrease = 100 - 99 = 1

Hence net percentage decrease
$=(\frac{1}{100}\times 100)\%=1\%$