Question

5. The total surface area of a right circular cone of slant height 20 cm is 384π cm2.
Calculate it's radius in cm


Please give me correct answer and if not possible then please ignore it , but don't give me wrong answers!!!!
​

Answer 1

Answer:

radius=12cm

Step-by-step explanation:

total surface area of cone =πr(l+r)

πr(l+r) =384πcm^2

π gets cancelled on both sides

r(20+r)=384

20r+r^2=384

r^2+20r-384=0 a quadratic equation

r^2+32r-20r-384=0

r(r+32)-12(r+32)=0

(r+32)+(r-12)=0

r=-32 r=+12

we should always take positive value

so r=12cm