BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

What is the sum of odd integers from 35 to 85, inclusive?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

Re: What is the sum of odd integers from 35 to 85, inclusive?

by Brent@GMATPrepNow » Sun Apr 19, 2020 6:17 am
BTGModeratorVI wrote: ↑
Sat Apr 18, 2020 9:18 am
 What is the sum of odd integers from 35 to 85, inclusive?

A) 1,560
B) 1,500
C) 1,240
D) 1,120
E) 1,100

Answer: A
Source: Official guide
We want: 35 + 37 + 39 + 41 + . . . . 79 + 81 + 83 + 85

Add the numbers in pairs, starting from the outside and working towards the middle, we get:
35 + 37 + 39 + 41 + . . . . 79 + 81 + 83 + 85 = (35 + 85) + (37 + 83) + (39 + 81) + . . .
= (120) + (120) + (120) + (120) + .....
= 120 times some integer

So, the desired sum must be DIVISIBLE by 120
Only one answer choice is divisible by 120

Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
GMAT Instructor
Posts: 8131
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

Re: What is the sum of odd integers from 35 to 85, inclusive?

by Scott@TargetTestPrep » Tue Apr 21, 2020 2:29 pm
BTGModeratorVI wrote: ↑
Sat Apr 18, 2020 9:18 am
 What is the sum of odd integers from 35 to 85, inclusive?

A) 1,560
B) 1,500
C) 1,240
D) 1,120
E) 1,100

Answer: A
Source: Official guide
The sum of the odd integers from 35 to 85, inclusive, is:

sum = avg x quantity

sum = (85 + 35)/2 * (85 - 35)/2 + 1

sum = 120/2 * 50/2 + 1

sum = 60 * 26 = 1560

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Post new topic Post Reply
• Page 1 of 1