A circular swimming pool is surrounded by a concrete wall 4m wide. If the area of the concrete wall surrounding the pool is 11/25 that of the pool, then the radius(in m) of the pool :

Explanation:

Let the swimming pool area = 25

Outer concrete area = 11

Total area = 25 + 11 = 36

area of total : area of pool

36 : 25

Ratio of radius

6:5

Difference 2 Unit = 4

5×4=20

Radius of swimming pool

=20m