Please help.. Find ∑x for the following set of numbers:4,5,7,8,10,11,13?

Question

I am stumped on this problem... please help me understand how to get the answer.. Thanks in advance...

Find ∑x for the following set of numbers:4,5,7,8,10,11,13

Answer 1

All you do is add the numbers up:

4+5+7+8+10+11+13 = 58

Answer 2

∑ (capital sigma) simply means the sum. If your question is ∑x for all x in {4, 5, 7, 8, 10, 11, 13} then it's just those seven numbers added up, which is 58.

But..... If the question is what is the sum of the integers from 1 up to (and including) x for each of the x in {4, 5, 7, 8, 10, 11, 13}, now it's a slightly different game. It can be shown that the sum of the integers from 1 to n is given by the expression
n(n+1)/2 so that the sum of the integers from 1 to 4 would be
4*(4+1)/2 = 10 (which you can easily verify)

Now you go through and work it out for all the values in the set {4, 5, 7, 8, 10, 11, 13}.

HTH

Doug

Answer 3

4+5+7+8+10+11+13=58