Ans: B
Let $\ell_0$ and $b_0$ be the original value of the length and the breadth of the rectangle respectively. Then we have
Let $\ell_0$ and $b_0$ be the original value of the length and the breadth of the rectangle respectively. Then we have
$\begin{array}{rcl}
\ell_0\times b_0 & = & \ell_0(1-20\%)\times b_0(1+k\%) \\
1 & = & 0.8(1+k\%) \\
1+k\% & = & 1.25 \\
k\% & = & 25\% \\
k & = & 25
\end{array}$
