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Hi,
number of board = n,
number of comittee = k (k person from n person) ==> k< n
each k send e-mail to board member who was not a member of the committee (n-k)
so total e-mail will be
k*(n-k) = 35 = 7*5

Is this the correct approach?
Thanks
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waritamorn
Hi,
number of board = n,
number of comittee = k (k person from n person) ==> k< n
each k send e-mail to board member who was not a member of the committee (n-k)
so total e-mail will be
k*(n-k) = 35 = 7*5

Is this the correct approach?
Thanks

Yes it is.
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* Each board member sent 1 email to "each of the other members" and we are given the total no. of emails. So we should ask, what should this total equal to?

Total no. of emails = No. of people sending the emails (k) * no. of people receiving the emails (n-k).
35 = k (n-k).
7*5 = k (n-k), so one of them is a multiple of 5 and one of them is a multiple of 7.
We know k<n, as we are choosing k from n, so k must be 5, which means, n-k=7 or n=12.

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TargetMBA007
* Each board member sent 1 email to "each of the other members" and we are given the total no. of emails. So we should ask, what should this total equal to?

Total no. of emails = No. of people sending the emails (k) * no. of people receiving the emails (n-k).
35 = k (n-k).
7*5 = k (n-k), so one of them is a multiple of 5 and one of them is a multiple of 7.
We know k<n, as we are choosing k from n, so k must be 5, which means, n-k=7 or n=12.

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Done. Thank you!
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This problem gave me a lot of trouble at first, but once I stopped focusing only on the math and thought logically about how the 35 emails are created, it clicked.

We’re told each committee member sends emails to everyone not on the committee. So how can we get a total of 35 emails?

The only product that makes sense is 5 × 7 = 35. But 7 isn’t one of the answer choices for n or k... so where is it coming from?

The only way to get it 7 is from 12-5. Now we have this narrowed down to to possible answers once we realize this.

And since the committee must be a subset of the board, k has to be less than n. Therefore n=12, k=5
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