Homework Help: surface and volume

Posted by lilman on Tuesday, May 1, 2012 at 8:18pm.

A glass vase weighs 0.12lb, how much does a similarly shaped vase of the same glass weigh if each dimension is 6 times as large?
possible answers;
4.32lbs
25.92lbs
0.72lbs
155.52lbs

These are the last problems I have and I can't figure them out can someone please help me?

The volume of a sphere is 5,000pim^3. What is the syrface area of the sphere to the nearest square meter?
possible answers;
3,033mm^2
62,832m2
195m^2
1,517m^2

Find the surface are of a sphere with a circumference of 155mm. Round to the nearest tenth.
possible answers;
7,647.4mm^2
608.6mm^2
24.7mm^2
3,823.7mm^2

Can someone plaese help me?

surface and volume - Reiny, Tuesday, May 1, 2012 at 8:59pm
Since the mass (weight) is related to its volume
and the volumes of similar objects are proportional to the cube of their sides ....

w/.12 = 6^3/1^3
w = .12(216)/1 = 25.92

2nd question:

V of sphere = (4/3)πr63
(4/3)πr^3 = 5000π
(4/3)r^3 = 5000 , I divided both sides by π
r^3 = 5000(3/4) = 3750
r = cuberoot(3750) = appr. 15.536..
SA = 4πr^2
= 3033 m^2 to the nearest whole number

(your answer has mm^2, it should be m^2, probably your typo )

3rd: try it yourself

hint: C = 2πr
2πr = 155 , solve for r and use the 2 formulas from above
surface and volume - lilman, Tuesday, May 1, 2012 at 9:30pm
I believe the answer for the 3rd one is 7,647.4 if I did it right

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