Question

Two similar pipes are shown.



The small pipe has a radius of 18 feet and a height of 21 feet while the large pipe has a height of 28 feet. What is the volume of the large pipe in terms of π?

5,376π ft3

18,432π ft3

6,804π ft3

16,128π ft3

Answer 1

how can i get the answer without the radius of the big cylinder

Answer 2

the key word is in the term "similar"

that means they have the same ratio of linear parts

Answer 3

21x = 28 when x=28/21

the radius of the larger one is then rx

Answer 4

there might be some fancy device to recall how volume changes with linear stuff, but i can never recall those relations

Answer 5

im still lost i have no idea how to solve this

Answer 6

"how can i get the answer without the radius of the big cylinder"; i just explained how to get the radius of the big cylindar

Answer 7

its 28/21 times bigger than the radius of the small one

Answer 8

ooo my bad..i see now

Answer 9

The volume of the smaller pipe is: pi * 18*18 * 21 = 6804 pi.
The larger pipe is similar to the smaller one and the scale factor from small to large is 21 to 28 which simplifies to 3/4.
If two solids are similar the cube of the scale factor is the ratio of the volumes.
(3/4) ^3 = 6804 pi / V where V is the volume of the larger solid
27/64 = 6804 pi / V
V = (64 * 6804 pi) / 27 = 16 128 pi --> ANS

Answer 10

lol, i knew there was a common factor, just couldnt see that it was 7 ;)

Answer 11

I can move my work if you are still working.

Answer 12

nah, its good. we both got a scalar of 3:4 mine just wasnt simplified

Answer 13

21x = 28

x = 28/21 = 4/3

18*4/3 = 24

Vb = 28(24^2) pi

Answer 14

@amistre64 whats the answer

Answer 15

The answer is the last one