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∛(328 - 800 - 48) is [#permalink]
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GMATPrepNow wrote:
(328 - 800 - 48) is

A) Between -4 and -5
B) Between -5 and -6
C) Between -6 and -7
D) Between -7 and -8
E) Less than -8


Another approach is to use a nice rule that says (ab) = (a)(b)
We'll also recognize that we can factor out an 8 (and we happens to know that 8 = 2)


We get: (328 - 800 - 48) = [8(41 - 100 - 6)
= [(8)(-65)]
= (8)(-65) [once we apply the above rule]
= (2)(-65)

Hmmm, what about (-65)?

Well we know that (-64) = -4
And we know that (-125) = -5
Since -65 lies BETWEEN -64 and -125, we know that (-65) lies between -4 and -5
So, let's say that (-65) = -4.something

This means that (2)(-65) = (2)(-4.something) = some number that's LESS THAN -8

Answer: E

Originally posted by BrentGMATPrepNow on 04 Nov 2016, 11:06.
Last edited by BrentGMATPrepNow on 21 Sep 2021, 17:56, edited 1 time in total.
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Re: ∛(328 - 800 - 48) is [#permalink]
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\sqrt{(328 - 800 - 48} = \sqrt{-520}

since -8^3 = -512

\sqrt{-520} is less than \sqrt{- 8}

hence E
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Re: ∛(328 - 800 - 48) is [#permalink]
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GMATPrepNow wrote:
(328 - 800 - 48) is

A) Between -4 and -5
B) Between -5 and -6
C) Between -6 and -7
D) Between -7 and -8
E) Less than -8

There are a few different ways to solve this one.
*Kudos for all correct solutions


\(∛(328 - 800 - 48)\)= ∛(-520)

the prime factorization of 520 is \(2^4*5*7\)

therefore the expression is equal to \(-2*∛(2*5*7)= -2*∛70\)

as 70 is very close to 64 which is 4^3 the value of ∛70 is a little bit higher than 4

therefore \(∛(328 - 800 - 48)>-2*4\)\(=-8\)

ANSWER E
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Re: ∛(328 - 800 - 48) is [#permalink]
Expert Reply
GMATPrepNow wrote:
(328 - 800 - 48) is

A) Between -4 and -5
B) Between -5 and -6
C) Between -6 and -7
D) Between -7 and -8
E) Less than -8



We can start by combining the values in the parenthesis:

∛(328 - 800 - 48) = ∛-520

Since 8^3 = 512 and 9^3 = 729, (-8)^3 = -512 and (-9)^3 = -729. Since -520 is between -729 and -512, ∛-520 is between -9 and -8, and thus ∛-520 is less than -8.

Answer: E
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Re: (328 - 800 - 48) is [#permalink]
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Re: (328 - 800 - 48) is [#permalink]
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