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If each term in the sum a1+a2+a3+...+an is either 7 or 77 and the sum

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Joined: 20 Aug 2018
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Re: If each term in the sum a1+a2+a3+...+an is either 7 or 77 and the sum  [#permalink]

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New post 24 Nov 2018, 18:51
There are a few different approaches.

A video explanation of two of them can be found here:
https://www.youtube.com/watch?v=Vcl1CXco3jk

One approach is to think about the maximum and minimum number of 7s we would need in order to reach a sum of 350. The maximum is 350/7 = 50, but 50 isn't an answer choice. We need a number that's lower than 50, so lets find the second-highest number by subtracting a 77 from 350

350 - 77 = 273

273/7 = 39, i.e. our list of numbers could have a 77 and thirty-nine "7s" and the sum would be 350

39 is the correct answer choice. Answer B

The video covers this approach and a second one, as well.
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Re: If each term in the sum a1+a2+a3+...+an is either 7 or 77 and the sum  [#permalink]

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New post 01 Nov 2019, 11:12
Great question, and thanks for the explanation Bunuel!
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Re: If each term in the sum a1+a2+a3+...+an is either 7 or 77 and the sum   [#permalink] 01 Nov 2019, 11:12

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