In x + 2 years (Plug in ans approach)

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melguy: Master | Next Rank: 500 Posts; Posts: 335; Joined: Mon Mar 21, 2011 11:31 pmFollowed by: 2 members; Location: Australia / India; Thanked: 37 times

by melguy » Sat Aug 24, 2013 9:43 pm

Hello

I want to solve this problem by plugging in back the answer choices. I am getting confused with (Joe was x years old 6 years ago). Please help with the problem. Thanks.

In x + 2 years, Joe's age will be double what it was x - 7 years ago. If Joe was x years old 6 years ago, how old will Joe be in 3 years?

9
12
15
18
21

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Source: Beat The GMAT — Problem Solving | Sat Aug 24, 2013 9:43 pm

vinay1983: Legendary Member; Posts: 643; Joined: Wed Aug 14, 2013 4:27 amFollowed by: 7 members; Thanked: 48 times

by vinay1983 » Sat Aug 24, 2013 10:46 pm

Hmmm i could arrive at this:

x+2=2(x-7)..........(1)

Joe's age - 6 = x....(2)

Joe + 3 = ?

You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Sun Aug 25, 2013 3:41 am

In x + 2 years, Joe's age will be double what it was x - 7 years ago. If Joe was x years old 6 years ago, how old will Joe be in 3 years?

9
12
15
18
21

We can plug in the answers choices, which represent Joe's age in 3 years.

Answer choice C: 15
Joe's age now = 15-3 = 12.
6 years ago, Joe's age = x = 12-6 = 6.
In x + 2 years, Joe's age will be double what it was x - 7 years ago.
x-7 = -1.
Too small.
Eliminate A, B and C.

Answer choice D: 18
Joe's age now = 18-3 = 15.
6 years ago, Joe's age = x = 15-6 = 9.
In x + 2 years, Joe's age will be double what it was x - 7 years ago.
x-7 = 9-7 = 2.
2 years ago, Joe's age = 15-2 = 13.
x+2 = 9+2 = 11.
In 11 years, Joe's age = 15+11 = 26.
Since 26 is double 13, success!

The correct answer is D.

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