The area of a square is three-fifths the area of a rectangle. The length of the rectangle is 25 cm and its breadth is 10 cm less than its length. What is the perimeter of the square ?

Answer: Option B

Length of rectangle = 25 cm
Breadth of rectangle = 15 cm
Area of rectangle :
$$\begin{array}{rl}& =\left(25\times 15\right)c{m}^2\\ & =375cm\end{array}$$
Area of square :
$$\begin{array}{rl}& =\left(\frac{3}{5}\times 375\right)c{m}^2\\ & =225c{m}^2\end{array}$$
Side of square :
$$\begin{array}{rl}& =\sqrt{225}cm\\ & =15cm\end{array}$$
Perimeter of square :
$$\begin{array}{rl}& =\left(4\times 15\right)cm\\ & =60cm\end{array}$$