is sphere(esp surface areaof sphere) tested in GMAT ?

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goelmohit2002: Legendary Member; Posts: 1799; Joined: Wed Dec 24, 2008 3:03 amFollowed by: 2 members; Thanked: 36 times

by goelmohit2002 » Wed Sep 16, 2009 9:55 pm

Hi All,

Can someone please tell is sphere properties(esp surface area of sphere) tested in GMAT....if yes then can someone please point me to a problem that tests sphere concept....

I checked Manhattan strategy guide of geometry....

But it does not talk about sphere at all....does it mean that spheres are not in the course of GMAT ?

Thanks
Mohit

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Source: Beat The GMAT — Problem Solving | Wed Sep 16, 2009 9:55 pm

xcusemeplz2009: Master | Next Rank: 500 Posts; Posts: 399; Joined: Wed Apr 15, 2009 3:48 am; Location: india; Thanked: 39 times

by xcusemeplz2009 » Wed Sep 16, 2009 11:34 pm

in my gmatprep i have faced question from ellipse ; that made me to learn each and every formulae from maths as i have seen tough problems usually needs remembring the formula only.

but mensuration has dozen of formula which is difficult remember , i will suggest to remember the area, sirface area and volume fofrmula at least .

It does not matter how many times you get knocked down , but how many times you get up

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goelmohit2002: Legendary Member; Posts: 1799; Joined: Wed Dec 24, 2008 3:03 amFollowed by: 2 members; Thanked: 36 times

by goelmohit2002 » Wed Sep 16, 2009 11:43 pm

xcusemeplz2009 wrote:in my gmatprep i have faced question from ellipse ; that made me to learn each and every formulae from maths as i have seen tough problems usually needs remembring the formula only.

but mensuration has dozen of formula which is difficult remember , i will suggest to remember the area, sirface area and volume fofrmula at least .

if you remember...can you please point to the question that you encountered of ellipse.

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maihuna: Legendary Member; Posts: 1578; Joined: Sun Dec 28, 2008 1:49 amFollowed by: 9 members; Thanked: 82 times; GMAT Score:720

by maihuna » Sun Sep 20, 2009 10:37 am

Phobus, one of the satellites of Mars, revolves about Mars at a distance of approximately
5,800 miles from the center of Mars and approximately 3,700 miles from the surface of
Mars. If it is assumed that Mars is spherical and the orbit of Phobus is circular, what is
the approximate circumference, in miles, of Mars at its equator?
A. 2,100Ï€
B. 4,200Ï€
C. 7,400Ï€
D. 9,500Ï€
E. 190,000Ï€

Charged up again to beat the beast

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goelmohit2002: Legendary Member; Posts: 1799; Joined: Wed Dec 24, 2008 3:03 amFollowed by: 2 members; Thanked: 36 times

by goelmohit2002 » Sun Sep 20, 2009 10:53 am

maihuna wrote:Phobus, one of the satellites of Mars, revolves about Mars at a distance of approximately
5,800 miles from the center of Mars and approximately 3,700 miles from the surface of
Mars. If it is assumed that Mars is spherical and the orbit of Phobus is circular, what is
the approximate circumference, in miles, of Mars at its equator?
A. 2,100Ï€
B. 4,200Ï€
C. 7,400Ï€
D. 9,500Ï€
E. 190,000Ï€

thanks....is this a GPrep or any official source question ?

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sun Sep 20, 2009 3:41 pm

goelmohit2002 wrote:
maihuna wrote:Phobus, one of the satellites of Mars, revolves about Mars at a distance of approximately
5,800 miles from the center of Mars and approximately 3,700 miles from the surface of
Mars. If it is assumed that Mars is spherical and the orbit of Phobus is circular, what is
the approximate circumference, in miles, of Mars at its equator?
A. 2,100Ï€
B. 4,200Ï€
C. 7,400Ï€
D. 9,500Ï€
E. 190,000Ï€
thanks....is this a GPrep or any official source question ?

While this question includes the word "sphere," it doesn't really test concepts related solely to spheres. Here, we can think of a point (Phobus) that is 5800 miles from the center of a circle (Mars) and 3700 miles from the edge of the circle (Mars).
So, the radius of the circle (Mars) is 2100 miles (5800-3700=2100). So, the circumference of the circle is 2(pi)r = (2)(pi)(2100) = 4200pi

To answer your original question, all you need to know is what a sphere is (it has a center and radius). You aren't required to know how to find its volume or surface area.

Brent Hanneson - Creator of GMATPrepNow.com

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