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Which of the following sets contain numbers that are factors of M, if

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Math Expert
Joined: 02 Sep 2009
Posts: 52285
Which of the following sets contain numbers that are factors of M, if  [#permalink]

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21 Dec 2017, 03:03
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Question Stats:

100% (03:55) correct 0% (00:00) wrong based on 3 sessions

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Which of the following sets contain numbers that are factors of M, if M is the sum of all integers from 21 to 85, inclusive?

A. (5, 7)
B. (2, 65)
C. (1, 13)
D. (3, 17)
E. (2, 9)

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Re: Which of the following sets contain numbers that are factors of M, if  [#permalink]

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21 Dec 2017, 05:08
Bunuel wrote:
Which of the following sets contain numbers that are factors of M, if M is the sum of all integers from 21 to 85, inclusive?

A. (5, 7)
B. (2, 65)
C. (1, 13)
D. (3, 17)
E. (2, 9)

M is the sum of all integers from 21 to 85 = 21+22+23+......+85

Count of integers from 21 to 85 = 85 - 20 = 65

Sum of numbers in Arithmetic progression = [(first term + Last Term)/2] * Number of terms

i.e. M = (21+85)*65/2 = 3445

Now, 3445 = 5*689 = 5*13*53

Bunuel : The question should be "Which of the following sets contains PRIME numbers that are factors of M"

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This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: Which of the following sets contain numbers that are factors of M, if &nbs [#permalink] 21 Dec 2017, 05:08
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