What is the sum of the odd integers from 45 to 65, inclusive

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AAPL: Moderator; Posts: 2644; Joined: Sun Oct 29, 2017 2:08 pmFollowed by: 2 members

by AAPL » Fri Dec 20, 2019 6:32 pm

Economist GMAT

What is the sum of the odd integers from 45 to 65, inclusive?

A. 495
B. 550
C. 555
D. 600
E. 605

OA E

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Source: Beat The GMAT — Problem Solving | Fri Dec 20, 2019 6:32 pm

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Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 amFollowed by: 34 members; Location: Grand Central / New York; Thanked: 470 times

by Jay@ManhattanReview » Mon Dec 23, 2019 1:21 am

AAPL wrote:Economist GMAT

What is the sum of the odd integers from 45 to 65, inclusive?

A. 495
B. 550
C. 555
D. 600
E. 605

OA E

From 45 to 65 there are 21 integers, out of which there are 11 odd and 10 even integers.

Average of odd integers from 45 to 65 = (45 + 65)/2 = 55. Thus, the sum of the odd integers from 45 to 65, inclusive = 55*11 = 605.

The correct answer: E

Hope this helps!

-Jay
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Scott@TargetTestPrep: GMAT Instructor; Posts: 8152; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Sat Dec 28, 2019 8:13 pm

AAPL wrote:Economist GMAT

What is the sum of the odd integers from 45 to 65, inclusive?

A. 495
B. 550
C. 555
D. 600
E. 605

OA E

We can use the formula sum = average x quantity

average = (greatest + smallest)/2 = (65 + 45)/2 = 110/2 = 55

quantity = (65 - 45)/2 + 1 = 11. This means that there are 11 odd integers between 45 and 65, inclusive.

So the sum is 55 x 11 = 605.

Answer: E

Scott Woodbury-Stewart
Founder and CEO
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