The sum of the first 50 positive even integers is 2550. What is the sum of even integers from 102 to 200 inclusive?
- 5100
- 7550
- 10100
- 15500
- 20100
- 5100
- 7550
- 10100
- 15500
- 20100
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For any set of uniformly spaced integers, the average of the integers = (Largest integer + Smallest integer)/2finance wrote:The sum of the first 50 positive even integers is 2550. What is the sum of even integers from 102 to 200 inclusive?
wow I loved this approach...))thank u both guys for ur explanations...I tried to use the first approach but I was not sure whether the rule of" sum of first and last over 2"was for consecutive numbers only or for evenly distributed numbers. Both ways are clear to me now.gmatboost wrote:The "clever approach" which I think is the one used in the OG to explain this is also worth thinking about.
Each number in the bigger list (102, 104, ... 200)
is 100 bigger than the corresponding number in the smaller list (2, 4, ... 100)
So, since there are 50 numbers, the sum of the bigger list is 50*100 = 5000 bigger.
2550 + 5000 = 7550.