It should not matter what order you add them in so I will go strait down on a row of 10x1

(1

2)=1+1=2

(3

4)=3+3=6

(5

6)=5+5=10

(7

8)=7+7=14

(9

10)=9+9=18

You are really only adding every odd number to itself which goes up by four past 2.

So the sum should equal added twice all the odd numbers from 1 to the number of numbers divided by two.

So the equation for a 10x1 should be:

So you should now have to repeat this 10 time right?

SO 10(50)=500