Question

Two numbers $a$ and $b$ are inversely proportional to each other. If $a$ increases by $100\%$, then $b$ decreases by:

Accepted Answer

E. Since $a \cdot b = k$, if $a$ increases by $100\%$, the new $a' = 2a$. Then $b' = \frac{k}{2a} = \frac{b}{2}$. Percentage decrease in $b$ is $\frac{b - b/2}{b} 	imes 100\% = 50\%$.

Inverse Proportion Percentage Change

Explanation

Practise this under exam conditions