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 ?

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