Question

A cylindrical metal pipe has a diameter of 20 millimeters and a height of 21 millimeters. A cylindrical hole cut out of the center has a radius of 6 millimeters.Which expressions represent the volume of metal needed, in cubic millimeters, to make the pipe? Check all that apply.
options:



21π(10)2 – 21π(6)2



π(20)2(21) – π(6)2



2,100π – 756π



7,644π



1,344

Answer 1

Answer:

• 21π(10)^2 – 21π(6)^2
• 2,100π – 756π

Step-by-step explanation:

The volume of metal is the difference of the overall volume of the cylinder and the volume of the hole in it. The formula for the volume of a cylinder is ...

... V = π·r^2·h . . . . . radius r and height h

For the overall dimensions, the radius is half the diameter, so is 10 mm. The hole is said to have a radius of 6 mm. The overall "height" is 21 mm, so the volume in mm³ will be ...

... V_overall -V_hole = π(10)^2(21) -π(6)^2(21)

... = 21π·10^2 -21π·6^2 . . . . . . . matches the first selection

... = 2100π -756π . . . . . . . . . . . matches the third selection

... = 1344π . . . . . . . . . . . . . . . . doesnt' match any selection

Answer 2

Answer:

1/A : 21π(10)^2 – 21π(6)^2

3/C : 2,100π – 756π

Step-by-step explanation:

Just took the test on edge : ) Hope this helps !