Leigh,

Consider the way that Gauss showed us how to sum an arithmetic sequence. You can see an example in our response to a previous question. Your example is an arithmetic sequence so there is some number d that you add to each term to obtain the next term. The middle term of a 15 term sequence is 92 so this is the 8^th term. The last term is 7 terms further along in the sequence so it is 92 + 7d. Likewise the first term is 7 terms before the 8^th term so it is 92 - 7d. Thus the sum of the first and last term is 92 - 7d + 92 + 7d = 92 + 92 = 184.

Can you now use Gauss' technique to find the sum of the sequence?

Penny