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If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the

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Joined: 20 May 2020
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If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the  [#permalink]

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New post 14 Jul 2020, 14:58
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If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the sum equals 350, which of the following could be equal to n ?

A. 38
B. 39
C. 40
D. 41
E. 42
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Re: If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the  [#permalink]

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New post 14 Jul 2020, 15:14
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vpsu wrote:
If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the sum equals 350, which of the following could be equal to n ?

A. 38
B. 39
C. 40
D. 41
E. 42


We can make a table of the number of 7's and 77's needed to build up to 350. Note that we have to exchange one 77 for eleven 7's.

Let's start with the base case of 50 * 7 = 350. Then we can also have 39*7 + 1*77 = 350, or 28*7 + 2*77 = 350. The total number of terms will drop by 10 for every additional 77 becasue +1 - 11 = -10.

Thus our possible answers for the number of terms are 50, 40, 30, 20, and 10.

Ans: C
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Re: If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the  [#permalink]

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New post 14 Jul 2020, 21:17
vpsu wrote:
If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the sum equals 350, which of the following could be equal to n ?

A. 38
B. 39
C. 40
D. 41
E. 42


This question is discussed here: https://gmatclub.com/forum/if-each-term ... 93974.html In case of questions please post there. Hope it helps.

Also, please read carefully and follow our posting rules: https://gmatclub.com/forum/rules-for-po ... 33935.html Thank you.

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Re: If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the   [#permalink] 14 Jul 2020, 21:17

If each term in the sum a1 + a2 + ... + an is either 7 or 77 and the

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