74.8k views
2 votes
Find the diameter of the base of a right cylinder if the surface area is 128(pi) and the height is 12cm.

1 Answer

3 votes

d=2r\\ A=128 \pi \\ A=2 \pi r^(2) +2 \pi rh \\\\ 2 \pi r^(2) +2 \pi rh = 128 \pi \\ 2 r^(2) +2rh = 128\\ 2 r^(2)+24r-128=0\\ r^(2)+12r-64=0\\ delta=400\\ r_(1/2) = -16/4 \\ r=4cm\\ d=8cm\\

Radius / diameter as a length cannot be negative, that's why '-16' is wrong.
User Drfloob
by
7.7k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories