The total surface area of a right circular cylinder is 628 ⁴⁄₇ cm². If its radius is 4 cm, then the height (rounded off to the nearest whole number) of the cylinder is equal to:
(Take π = 22⁄7)
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e 21 cm.
Total Surface Area = 2πr² + 2πrh
TSA = 2 × 22/7 × 4² + 2 × 22/7 × 4 × h
TSA = 2 × 22 × 16/7 + 176h/7
TSA = 704/7 + 176h/7
⇒ 4396/7 = 704/7 + 176h/7
⇒ 4396 = 704 + 176h ⇒ 3692 = 176h
⇒ h = 3692 ÷ 176 = 20.95 or 21 cm