Homework Help: surface area and volume

Posted by lilman on Sunday, April 29, 2012 at 11:15am.

I really need some help, I don't fully understand. Exspecially with fractions, don't know how to enter them on calculator.

1. What is the approximate volume of the sphere?

524 mł (my choice)
1,000 mł
1,256 mł
1,570 mł

2. What is the approximate surface area of the sphere?

225 yd2
707 yd2
1,767 yd2 (my choice)
5,301 yd2

3. What is the approximate volume of the sphere if the surface area is 482.8 mm˛?

998 mmł
1,126 mmł
2,042 mm ł
2,993 mmł
I don't understand this one.

4. What is the approximate surface area of the sphere?

342.3 km2
451.9 km2
903.4 km2
2,713 km2
Don't understand.

5. What is the approximate radius of a sphere whose volume is 1,349 cmł?

5.7 cm
6.9 cm
11 cm
14.7 cm
Don't understand.

surface area and volume - incomplete - Ms. Sue, Sunday, April 29, 2012 at 11:40am
.
surface area and volume - Reiny, Sunday, April 29, 2012 at 12:59pm
you are dealing with two equations

1. surface area of sphere = 4π r^2
2. volume of sphere = (4/3)π r^3

notice all you need is the radius.
Since we cannot see your diagrams, #1, and #2 cannot be checked

3. given 4πr^2 = 482.8
r^2 = 482.8/(4π) = 38.42
r= √38.42 = 6.198
volume = (4/3)πr^3 = 997.53 , looks like a)

4.
you must have the radius given to you, just plug into the formula

5.
(4/3)πr^3 = 1349
r^3 = 1349/((4/3)π) = 322.05
r= (322.05)^(1/3) , the cube root of 322.05
= 6.85 (looks like b) )

fractions are really just divisions
e.g. 3/4 = 3 ÷ 4 = .75
you calculator should have a key for π

for powers look for key such as y^x or a variation of that

to do 322.05^(1/3) I entered

322.05
y^x
(1/3)
=
to get 6.85447...

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