Question

The total surface area of a right circular cylinder of height 9m is 440 sq. meter.Find the radius of the cylinder. (Take π = 22/7)

Answer 1

Total surface area of right circular cylinder = $2\pi r(r+h)$

Given that $2\pi r(r+h)=440m^2$

2× $\frac{22}{7}$ $\times$ r (9 +r) = 440 [As h=9]

solving quadratic equation,

$r^2$ + 9r - 70 = 0

$r^2$ + 14 r -5r -70 = 0

r(r +14)-5(r +14) = 0

r = 5, r = -14

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