Question

the radius and height of a cylinder are in the ratio 5:7 the volume is 4400 cm³ find the radius of the cylinder

Answer 1

let,

radius = r = 5x

height=  h = 7x

volume = v = 550cm³

V = πr²h

550 = 22/7 × (5x)² × 7x

550 = 22 × 25 x³

      = 550 x3

x³ = 1

x= 1

therefore, length = 5x = 5×1= 5 cm

                height = 7x = 7×1 = 7 cm

c.s.a of cylinder = 2 π r h

                         = 2 × 22/7 × 5 × 7

                         = 220 cm²

t.s.a of cylinder = 2πr(r+h)

                        = 2 ×22/7× 5(5 +7)

                        = 377.14 cm²

ratio of c.s.a to t.s.a = 220 :377.14

                                = 7 :12