Geometry

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talaangoshtari: Master | Next Rank: 500 Posts; Posts: 154; Joined: Wed May 21, 2014 4:29 amFollowed by: 1 member; Thanked: 8 times

by talaangoshtari » Wed Jul 22, 2015 5:09 am

A sector of a circle of radius 5 cm is recast into a right circular cone of height 4 cm. What is the volume of the resulting cone?

A. 12Ï€ cm3
B. 100Ï€ cm3
C. 33Ï€ cm3
D. 32Ï€ cm3
E. 4Ï€ cm3

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Source: Beat The GMAT — Problem Solving | Wed Jul 22, 2015 5:09 am

Jim@StratusPrep: MBA Admissions Consultant; Posts: 2279; Joined: Fri Nov 11, 2011 7:51 amFollowed by: 266 members; Location: New York; Thanked: 660 times; GMAT Score:770

by Jim@StratusPrep » Wed Jul 22, 2015 5:18 am

This is essentially saying that you are to calculate the volume of a cone with a radius of 5 and height 4.

1/3Ï€r^2h = = 1/3(100Ï€) = 33Ï€

However, not likely a phrasing you will see on the GMAT.

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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 » Wed Jul 22, 2015 5:30 am

talaangoshtari wrote:A sector of a circle of radius 5 cm is recast into a right circular cone of height 4 cm. What is the volume of the resulting cone?

A. 12Ï€ cm3
B. 100Ï€ cm3
C. 33Ï€ cm3
D. 32Ï€ cm3
E. 4Ï€ cm3

On the GMAT, you don't need to know the formula for the volume of a cone.

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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by [email protected] » Wed Jul 22, 2015 8:13 am

Hi talaangoshtari,

When it comes to geometric 'solids', you DO need to know the formulas for Volume and Surface area for rectangular solids, cubes (which are just a specific type of rectangular solid) and cylinders. You do NOT need to memorize anything involving spheres, cones or pyramids. In the rare situation in which you deal with one of those shapes, you'll be given the necessary formula(s) to work with.

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nikhilgmat31: Legendary Member; Posts: 518; Joined: Tue May 12, 2015 8:25 pm; Thanked: 10 times

by nikhilgmat31 » Wed Jul 29, 2015 3:23 am

what recast means here.
Does it means volume of sector of sphere is casted to make a cone.

or I am think too much.

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