Cube Root Question

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Aaring23: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Tue Apr 15, 2008 12:18 pm

by Aaring23 » Thu Apr 24, 2008 12:26 pm

Hey guy's I was wondering if someone could help me out with this problem. Here is the problem.

The value of Cube root -89 is.

Answer between -4 and -5.

Any help will be appreciated. Thank you.

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Source: Beat The GMAT — Problem Solving | Thu Apr 24, 2008 12:26 pm

luvaduva: Senior | Next Rank: 100 Posts; Posts: 84; Joined: Tue Feb 05, 2008 8:52 pm; Thanked: 8 times

by luvaduva » Thu Apr 24, 2008 5:58 pm

Negative cubes and cube roots have negative values.

-89 does have a cube root of around -4.46, but it is not an integer. The range of integers that the cube root of -89 lies between is:

-4 and -5

-4^3 = -64
-5^3 = -125

HTH

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AleksandrM: Legendary Member; Posts: 566; Joined: Fri Jan 04, 2008 11:01 am; Location: Philadelphia; Thanked: 31 times; GMAT Score:640

by AleksandrM » Fri Apr 25, 2008 9:42 am

Aaring,

This kind of a problem is useful to know because you will sometimes be asked to find a sqroot or cbroot of a number that does not have a perfect sqroot or cbroot. For example, what is the sqroot of 41. The way to look at it is as follows: 6 squared = 36 and 7 squared = 49. So the answer is somewhere between 6 and 7. Since 42 is closer to 36 than it is to 49, a good approximation might be 6.4.

https://second-lap.blocked/

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