Hectic Maths Probs !!!

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Almasha: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Mon Oct 17, 2011 5:43 am

Hectic Maths Probs !!!

by Almasha » Mon Oct 17, 2011 6:02 am

Hi
Can anyone help me by saving my time??

Luqman is 67. His son Rehan is 29. In how many years will Rehan be exactly half his father's age?
A. 2
B. 5
C. 7
D. 9
E. 12

Wanna know the answer alongwith accessible explaination.
Regards

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Source: Beat The GMAT — Problem Solving | Mon Oct 17, 2011 6:02 am

shankar.ashwin: Legendary Member; Posts: 966; Joined: Sat Jan 02, 2010 8:06 am; Thanked: 230 times; Followed by:21 members

by shankar.ashwin » Mon Oct 17, 2011 6:07 am

Just substitute numbers and find out which satisfies.

Start with C : L - 67+7=74 and R - 29+7 = 36 (36*2 = 72) Need a bigger Number
Try D: L: 67+9=76 and R: 29+9=38 (38*2=76) Success

D

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Abhishek009: Master | Next Rank: 500 Posts; Posts: 359; Joined: Wed Mar 11, 2009 4:37 am; Location: Kolkata, India; Thanked: 50 times; Followed by:2 members

by Abhishek009 » Mon Oct 17, 2011 6:24 am

Almasha wrote:Hi
Can anyone help me by saving my time??

Luqman is 67. His son Rehan is 29. In how many years will Rehan be exactly half his father's age?
A. 2
B. 5
C. 7
D. 9
E. 12

Wanna know the answer alongwith accessible explaination.
Regards

In how many years will Rehan be exactly half his father's age - Here the key point is we must consider that both of them grows at the same time , that is both of them grows...

Let the number of years be x.

Now further it is given - Rehan be exactly half his father's age , here both of them grows old at the same time and after a certain number of years Rehan is half the age of his father...

(67 + x )/2 = 29 + x

67 + x = 58 + 2x

9 = x

Abhishek