Gmat Prep - Sum of integers question

[ssy]

The sum of the first 50 positive integers is 2550. What is the sum of the even integers from 100 to 200, inclusive?

5100
7550
10100
15500
20100

7550

[samirpandeyit62]

The sum of the first 50 positive integers is 2550. What is the sum of the even integers from 100 to 200, inclusive?

this question has been posted many times now

It should beThe sum of the first 50 even positive integers is 2550.

so sum of 100 -200 even integers is

100 + 102 ... 200

100 + 100+2 + 100 +4 + ....100 + 100

= 100*50 + 2+4.....100

= 5000 + 2550 =7550

[gmatguy16]

the question says sum of first 50 positive integers, does not say sum of first 50 [b]even[/b] positive integers,something is wrong with the question i guess...

[samirpandeyit62]

Hey gmatguy6 the sum of first 50 positive nos will not be 2550, I've solved this same question before hence I could make out that.

[gmatguy16]

samir,i am sorry for the confusion ..
i meant the question says sum of first 50 positive integers which means ...1+2+3+4+5 ...=2550 and you have used sum of first 50 even integers as 2550

[samirpandeyit62]

Hi gmatguy16,
I've understood ur point man, but just evaluate if it is the sum of first 50 nos i.e 1+2+3.....+50 will it sum upto 2550

sum will be 50*51/2 which will not be 2550

actually this problem was solved some time back on this forum so I just could remember from that question that it was the sum of the first 50 +ve even integers which will be 50*51 = 2550 & solved it accordingly.

[rainbowpo]

I also think there is something wrong with the original question

[hillzheng]

It is 7550

[CITI29]

I think the question is correct

sum of 100 -200 even integers is

100 + 102 ... 200

100 + 100+2 + 100 +4 + ....100 + 100

= 100*50 + 2+4.....100
= 100*50 + 2(1+2.....50)
= 5000 + 2*2550
= 5000+ 5100
= 10100

correct answer is C