1.  A cistern 6m long and 4 m wide contains water up to a depth of 1 m 25 cm. The total area of the wet surface is:
A. 49 m2
B. 50 m2
C. 53.5 m2
D. 55 m2

Answer: Option A

Explanation:

Area of the wet surface:

= [2(lb + bh + lh) - lb]
= 2(bh + lh) + lb
= [2 (4 x 1.25 + 6 x 1.25) + 6 x 4] m2
= 49 m2.