Question

I know the answer to this question, but I want to find a simpler way of doing it...



---Find the sum of the counting numbers from 1 to 25 inclusive. In other words, if S= 1+2+3+...+24+25, find the value of S.


Thanks!!!!!

Answer 1

It can also be designated as "S!", which is said as "S factorial." It means

S + (S-1) + (S-2)...3 + 2 + 1

Does that help? Thanks for asking.

Answer 2

S=325

Answer 3

Sorry, super late. You most likely wouldn’t see this, but whoever does, here is a shortcut.
n*(n + 1) n*a
———— = —— = n*b = x n + 1 = a
2 2 a/2 or 1/2*a = b

25*(25 + 1) 25*26 n*b = x
————— = ———— = 25*13 = 325
2 2

There is also a “rainbow” method.
Example: Find the sum of the counting numbers from 1 to 10 inclusive.
1 + 10 = 11
2 + 9 = 11
3 + 8 = 11
4 + 7 = 11
5 + 6 = 11

The method I put above the rainbow method is basically a more efficient version of the rainbow version. I hope this didn’t confuse you, and also hope this was helpful!
Best regards,
A young elementary schooler.