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= (\pi*r^2*h)/(3)=(\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= (a*b*h)/(3)`


`a=9ft`

`b=4ft`

`h=12ft`


`V= (4*9*12)/(3)=4*3*12=144 ft^3`

Answer: B