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GMATCLUB TEST Help M01

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Intern
Affiliations: Omicron Delta Kappa
Joined: 16 May 2011
Posts: 8

Kudos [?]: [0], given: 0

Schools: Union Graduate College, Howard, Quinnipiac University
GMATCLUB TEST Help M01 [#permalink]

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23 Jun 2011, 11:27
00:00

Difficulty:

(N/A)

Question Stats:

80% (00:34) correct 20% (00:00) wrong based on 5 sessions

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Today John is 3 times older than Mark. If in 13 years, John will be one year younger than twice the age of Mark on that day, how old is John today?
A. 13
B. 33
C. 36
D. 38
E. 39

I just cant understand how this was solved.
[Reveal] Spoiler: OA

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Current Student
Joined: 26 May 2005
Posts: 554

Kudos [?]: 244 [0], given: 13

Re: GMATCLUB TEST Help M01 [#permalink]

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23 Jun 2011, 11:35
adelabu44 wrote:
Today John is 3 times older than Mark. If in 13 years, John will be one year younger than twice the age of Mark on that day, how old is John today?
A. 13
B. 33
C. 36
D. 38
E. 39

I just cant understand how this was solved.

Its C
today john is 3 times mark , this means J = 3M...........................1
in 13 years
j = J + 13
M = M+13

John will be one year younger than twice the age of Mark on that day
J+13= 2(M+13)-1
j+13= 2m+25
from 1;
3m+13= 2m+25
m = 12
therefore j = 36

Kudos [?]: 244 [0], given: 13

Intern
Affiliations: Omicron Delta Kappa
Joined: 16 May 2011
Posts: 8

Kudos [?]: [0], given: 0

Schools: Union Graduate College, Howard, Quinnipiac University
Re: GMATCLUB TEST Help M01 [#permalink]

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23 Jun 2011, 11:39
! I see my mistake. I grouped (2M+13)-1 instead of 2(M+13)-1

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Director
Joined: 01 Feb 2011
Posts: 725

Kudos [?]: 147 [0], given: 42

Re: GMATCLUB TEST Help M01 [#permalink]

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23 Jun 2011, 20:32
today +13yrs

J =3M 3M+13

M M+13

Given after 13yrs john will be 1 year younger than twice mark's age

i.e 3M+13 = 2(M+13)-1

M=12

=>John's current age = 3M = 36

Answer is C.

Kudos [?]: 147 [0], given: 42

Re: GMATCLUB TEST Help M01   [#permalink] 23 Jun 2011, 20:32
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GMATCLUB TEST Help M01

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