Jill M. answered • 04/29/19
Retired Math Teacher
Volume Formula for a Cylinder= π X r2 X h Using h= 10 and r = 8 then the formula becomes:
π X (8)2 X 10 so the answer is 640π
Next use h = 5 and r = 4 π X (4)2 X 5 so the answer now becomes 80π
Now divide the top answer by the bottom answer 640π / 80π after dividing π by π, it cancels out.
now 640/80 = 8
So the volume is 8 times bigger before halving the h and r. Or the new volume is 1/8 the size of the original .
The WHY: r is cut in half that makes r squared equal to 1/2 X 1/2 which equals 1/4.
h is cut in half so take that 1/2 times the previous 1/4. That makes the volume 1/8 th.
Jill M.
Surface Area formula is 2 X pi X r (r +h) Use h = 10 and r = 8 again. Plug these in: 2 X pi X 8( 8 + 10) so 16pi (18) = 288 pi Once again change the r and h to 4 and 5: 2 X pi X 4( 4 + 5) to 8pi (9) = 72pi Again divide the 288pi/72pi = 4 WHY 2 X pi X 1/2 (1/2) That makes the new Surface area 1/4 the size of the original.04/29/19