Question

help me wit these 3 questions plz. A cone has a base radius of 7 centimeters and a height of 21 centimeters.   What is the volume of the cone?         A. 28π cm3       B. 49π cm3       C. 147π cm3       D. 343π cm3

Answer 1

1. Cone

$r=7cm$
$h=21cm$

$V= \frac{\pi*r^2*h}{3}=\frac{\pi*7^2*21}{3}=7^2*7*\pi=7^3\pi=343{\pi}cm^3$

Answer: D

2. Cylinder

$r=5ft$
$h=16ft$

$V= \pi*r^2*h=\pi*5^2*16=25*16\pi=400\pi ft^3$

Answer: A

3.Pyramid

In this case it will be

$V= \frac{a*b*h}{3}$

$a=9ft$
$b=4ft$
$h=12ft$

$V= \frac{4*9*12}{3}=4*3*12=144 ft^3$

Answer: B