The expenses of painting the inner curved surface of a cylindrical vessel 20 m deep is ₹4,400. If the painting rate is ₹40 per m2, find the total surface area (in m2) of the vessel correct to two places of decimals. (used = ).
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 114.81 m2.
Area painted = Expenses ÷ Rate = 4400 ÷ 40 = 110 m2
Curved surface area of cylinder = 2 × π × r × h
2 × 22/7 × r × 20 = 110
880r/7 = 110
r = (110 × 7) ÷ 880 = 770 ÷ 880 = 7 ÷ 8 = 7/8 m
Total surface area = 2 × π × r × h + 2 × π × r2
= 110 + 2 × 22/7 × (7/8)²
= 110 + 44/7 × 49/64
= 110 + 4.8125
= 114.8125 m2