Question

if the slant height is 7cm and total surface area is 147.84cm square found the radius

Answer 1

Given, total surface area = 147.84 cm²

Slant height = 7 cm

Total surface area of cone = π·r (r + s)

Where r is the base radius and s is the slant height.

-------------------------------------------------------------------------------------------------------------

Let of the base Radius = x

π·r (r + 7) = 147.84

22/7 r (r + 7) = 147.84

r (r + 7) = 147.84 * 7/22

r ( r + 7) = 47.04

r² + 7r - 47.04 = 0

r² - 4.2r + 11.2r - 47.04 = 0

r (r - 4.2) + 11.2 (r - 4.2) = 0

(r - 4.2) (r + 11.2) = 0

r = 4.2 and -11.2

ignoring negative value of r

we get r as radius = 4.2 cm

-------------------------------------------------------------------------------------------------------------