If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the foll - The Beat The GMAT Forum

If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the foll

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BTGModeratorVI: Legendary Member; Posts: 1223; Joined: Sat Feb 15, 2020 2:23 pmFollowed by: 1 member

by BTGModeratorVI » Sun Apr 05, 2020 9:03 am

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If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the following?

A. –2
B. 3
C. 3.5
D. 5
E. 7

Answer: B
Source: Kaplan

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Source: Beat The GMAT — Problem Solving | Sun Apr 05, 2020 9:03 am

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

Re: If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the

by Brent@GMATPrepNow » Sun Apr 05, 2020 3:51 pm

BTGModeratorVI wrote: ↑
Sun Apr 05, 2020 9:03 am
If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the following?

A. –2
B. 3
C. 3.5
D. 5
E. 7

Answer: B
Source: Kaplan

Given: 2x² + 6x = 8
Divide both sides by 2 to get: x² + 3x = 4
Subtract 4 from both sides to get: x² + 3x - 4 = 0
Factor: (x + 4)(x - 1) = 0
Solved to get: EITHER x = -4 OR x = 1

Since we're told that x > 0, we can be certain that x = 1

QUESTION: What is the average (arithmetic mean) of x + 2, 2x – 1, and x + 4?
If x = 1, then:
x + 2 = 1 + 2 = 3
2x - 1 = 2(1) - 1 = 1
x + 4 = 1 + 4 = 5

Average of 3, 1 and 5 = (3 + 1 + 5)/3
= 9/3
= 3

Answer: B

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8156; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

Re: If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the

by Scott@TargetTestPrep » Mon Apr 27, 2020 3:43 am

BTGModeratorVI wrote: ↑
Sun Apr 05, 2020 9:03 am
If x > 0 and 2x^2 + 6x = 8, then the average (arithmetic mean) of x + 2, 2x – 1, and x + 4 is equal to which of the following?

A. –2
B. 3
C. 3.5
D. 5
E. 7

Answer: B
Source: Kaplan

Let’s solve the given equation:

2x^2 + 6x - 8 = 0

x^2 + 3x - 4 = 0

(x - 1)(x + 4) = 0

x = 1 or x = -4

Since we are given that x > 0, then x = 1. So the average of x + 2, 2x – 1, and x + 4 is equal to

(3 + 1 + 5)/3 = 9/3 = 3

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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