Question

a cone of height 2.8 cm has a lateral surface area 23.10 cm^2.what is the radius of the base

Answer 1

lateral surface area = 23.10 cm²
l = √(h² + r²) =  √(7.84 + r²)
lateral surface area = π r l
so 
23.10 = 3.14 x r x √(7.84 + r²)
⇒  r x √(7.84 + r²) = 7.35
⇒7.84 + r² = 54.02 /r²
solving r we get 
r = 2.1003 cm