I cant seem to find the answer to this question:
Explain how to mentally solve the equation 99 + 98 + 97 + 96.....anll the way until One...using commutative associative and/or identitty properties
2006-09-14 14:43:42 · 3 answers · asked by theatreis4life 2 in Education & Reference ➔ Homework Help
This one's famous.
It's 99/2 x 100. (In other words, 4950).
Think about if you were adding up the numbers 1-100 in this way.
1+100 is 101.
2+99 is 101.
3+98 is 101.
You could keep doing this until you got to 49+50 or whatever it is, which would be doing this 50 times!
So it'd be 50 (half of 100) x 101 (100 +1).
The formula is n/2 x n+1.
2006-09-14 15:00:45 · answer #1 · answered by sarahg 3 · 0⤊ 0⤋
Well, I would solve it by taking away the 9,8,7, and the 6 and add them( taken away from the 90's). Then u add the 4 90's which is 360 and add that to 9+8+7+6(=30). So, the answer is 390. And i did that mentall, but i had to tell u how.....
2006-09-14 21:51:52 · answer #2 · answered by Kim 2 · 0⤊ 0⤋
sorry can't help you
2006-09-14 21:57:33 · answer #3 · answered by Amanda W 1 · 0⤊ 0⤋