The length and breadth of play ground are 36 m and 21 m respectively. Flag staffs are required to be fixed on all along the boundary at a distance of 3 m part. The number of flag staffs will be___________?

A. 37
B. 38
C. 39
D. 40

Explanation:

Perimeter = 2×(36+21) m = 114 m

Number of flag staffs = (114/3) = 38