Question

The total surface area of a right circular cylinder of height 9 m is 440 sq. meter. Find the radius of the cylinder. $(Take\pi =\frac{22}{7})$

• A. 2.5m
• B. 5m
• C. 7.5 m
• D. 10m

Answer 1

The correct option is B

5m

Given, height of the cylinder = 9 m
Total surface area of the cylinder = 440 $m^2$

Total surface area of right circular cylinder = 2π r(r+h) = 440 $m^2$ ... (i)

Putting h = 9 in the above equation, we get

$2\times \frac{22}{7}\times r\times (9+r)$ = 440
$r^2$ + 9r - 70 = 0
$r^2$ + 14r -5r -70 = 0
r(r +14) - 5(r +14) = 0
r = 5, r = -14

Since, length can’t be negative, r = 5 m