cube root of (-89)

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uptowngirl92: Master | Next Rank: 500 Posts; Posts: 447; Joined: Sun Apr 19, 2009 9:08 pm; Location: Kolkata,India; Thanked: 7 times; GMAT Score:670

by uptowngirl92 » Tue Nov 03, 2009 5:23 pm

The value of cube root of (-89) is..?

Between -9 and 10
Between -8 and -9
Between -4 and 5
Between -3 and 4
Undefined

...................

[spoiler=]Is'nt the root of any negative number undefined?[/spoiler]

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Source: Beat The GMAT — Problem Solving | Tue Nov 03, 2009 5:23 pm

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

Re: cube root of (-89)

by xcusemeplz2009 » Tue Nov 03, 2009 7:14 pm

uptowngirl92 wrote:The value of cube root of (-89) is..?

Between -9 and 10
Between -8 and -9
Between -4 and 5
Between -3 and 4
Undefined

...................

[spoiler=]Is'nt the root of any negative number undefined?[/spoiler]

IMHO
Sqrt of a -ve no. is imaginery,
but here its cube root
for this one i hope u have a typo in choice a) it should be -10

OA pls

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

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NikolayZ: Master | Next Rank: 500 Posts; Posts: 124; Joined: Thu Jun 18, 2009 5:33 am; Thanked: 35 times

by NikolayZ » Wed Nov 04, 2009 6:29 am

Well, still we can answer this question.

-89 is negative, hence the number^3=-89 must be negative too.
(-3)^3=-27
(-4)^3=-64
(-5)^3=-125,
Hence the cube root of (-89) must be in (-4;-5), the only segment that must include this number is A: (-9;10)

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sanjana: Master | Next Rank: 500 Posts; Posts: 182; Joined: Sun Aug 02, 2009 7:19 pm; Thanked: 18 times; GMAT Score:680

by sanjana » Wed Nov 04, 2009 9:16 am

The answer is between -4 and -5.

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heshamelaziry: Legendary Member; Posts: 869; Joined: Wed Aug 26, 2009 3:49 pmFollowed by: 3 members; Location: California; Thanked: 13 times

by heshamelaziry » Wed Nov 04, 2009 10:38 am

IMO -4, 5

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