Hi Christina,

Your sequence starts at 4 and then each term is 4 less then the previous term

4, 0, -4, -8, -12, ..., -148, -152, -156

Ignoring the first two terms for the moment the remaining terms are

-4 1, -4 2, -4 3, ..., -4 37, -4 38, -4 39

Thus there are 39 terms in that part of the sequence and hence there are 41 terms in the entire sequence.

The way to sum the terms is to do it twice, once frontwards and once backwards.

2sum =	4	+ 0	+ (-4)	+...	+ (-148)	+ (-152)	+ (-156)	+
	(-156)	+ (-152)	+ (-148)	+...	+ (-4)	+ 0	4

Now add down first, then across,

2sum =

152

+152

+152

+...

+152

+152

+152

Thus 2 sum = 152 41 = 6232 and therefore the sum is 3116.

Penny

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