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The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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25 Feb 2014, 00:07
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The Official Guide For GMAT® Quantitative Review, 2ND EditionThe sum of the ages of Doris and Fred is y years. If Doris is 12 years older than Fred , how many years old will Fred be y years from now, in terms of y ? (A) y  6 (B) 2y  6 (C) y/2  6 (D) 3y/2  6 (E) 5y/2  6 Problem Solving Question: 115 Category: Algebra Applied problems; Simultaneous equations Page: 76 Difficulty: 600 GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition  Quantitative Questions ProjectEach week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution. We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation. Thank you!
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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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25 Feb 2014, 00:07



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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25 Feb 2014, 02:12
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Let the ages of Fred and Doris be 'F' and 'D' respectively.
Sum of their ages = F+D = y Now since Doris is 12 years older than Fred , D=F+12 Therefore 2F+12=y thus F=y/2  6
'y' years from now Fred will be F=y/26+ y = 3y/2 6
Thus answer = Option (D)



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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25 Feb 2014, 22:15
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Let the ages of Doris and Fred be D and F respectively.
Given that, D + F = y & D = F + 12; F + 12 + F = y; 2F + 12 = y; 2F = y  12; F = y/2  6;
Now, since we are asked for Fred's age "y" years from now, we can add y to F: F + y = y + y/2  6; F + y = 3y/2  6;
Ans is (D).



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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26 Feb 2014, 02:06
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Option D. D+F=y And D=F+12 Therefore,2F+12=y Or F=(y12)/2 After y years,F=y+(y12)/2 F=3y/26



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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01 Mar 2014, 04:39



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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13 Apr 2014, 07:10
D+F = Y  First Equation. D=F+12  Second Equation how many years old will Fred be y years from now can be represented as (F+Y). As we need the answer in terms of Y , substitute Second Equation in First. F+12+F= Y; 2F+12=Y. 2F=Y12 F=Y12/2; Now F+Y in terms of Y is Y12/2 + Y = 3Y/2 6 ; Hence D



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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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13 Apr 2014, 20:34
Let age of Doris = d, then Age of Fred = yd .......... (1) Doris is 12 yrs older than Fred yd+12 = d 2d = y+12 \(d = \frac{y}{2} + 6\) ......... (2) Substituting value of d from (2) in (1) \(Age of Fred = y  (\frac{y}{2} + 6)\) \(= \frac{y}{2}  6\) Age of Fred after y yrs \(=\frac{y}{2}  6 + y\) \(= \frac{3y}{2}  6\) Answer = D
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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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11 Jun 2014, 14:41
It can be easily solved using smart numbers Doris = D, Fred = F Let's say D = 24 than F is 12 less = 12 > 24 + 12 = Y = 36; So in Y or 36 Years Fred will be 12 + 36 = 48 Plugin 36 for Y, in a right answer you schould get 48 > D (3*36)/26 = 48
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Re: The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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The sum of the ages of Doris and Fred is y years. If Doris [#permalink]
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09 Dec 2016, 03:46
BrainLab wrote: It can be easily solved using smart numbers Doris = D, Fred = F Let's say D = 24 than F is 12 less = 12 > 24 + 12 = Y = 36; So in Y or 36 Years Fred will be 12 + 36 = 48 Plugin 36 for Y, in a right answer you schould get 48 > D (3*36)/26 = 48 I tried this method and I am completely stumped. 3*36=108 26=4 108/4=27 not 48. Can somebody please explain what I am doing wrong?




The sum of the ages of Doris and Fred is y years. If Doris
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