You can put this solution on YOUR website! What is the sum of the odd intergers between 10 and 90?
The easy way:
There are 40 odd numbers from 10 to 90.
Group them in 10 pairs from the outside in. Each pair adds to 100.
11 + 89 = 100
13 + 87 = 100, etc
20 pairs * 100 = 2000
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PS It's integers, not intergers.
