If m=9^(xâˆ’1), then in terms of m, 3^(4xâˆ’2) must be which

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vinni.k: Master | Next Rank: 500 Posts; Posts: 421; Joined: Sun Apr 17, 2011 4:27 amFollowed by: 2 members; Location: India; Thanked: 6 times; GMAT Score:620

by vinni.k » Tue Dec 24, 2013 8:43 am

If m=9^(xâˆ’1), then in terms of m, 3^(4xâˆ’2) must be which of the following?

A. m/3
B. 9m
C. 9m^2
D. m^2/3
E. m^2/9

OA is C

Please explain.

Thanks & Regards
Vinni

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Source: Beat The GMAT — Problem Solving | Tue Dec 24, 2013 8:43 am

Uva@90: Master | Next Rank: 500 Posts; Posts: 490; Joined: Thu Jul 04, 2013 7:30 amFollowed by: 5 members; Location: Chennai, India; Thanked: 83 times

by Uva@90 » Tue Dec 24, 2013 8:54 am

vinni.k wrote:If m=9^(xâˆ’1), then in terms of m, 3^(4xâˆ’2) must be which of the following?

A. m/3
B. 9m
C. 9m^2
D. m^2/3
E. m^2/9

OA is C

Please explain.

Thanks & Regards
Vinni

Hi Vinni,
Just take some simple value and solve it.

Example Let X =2
m=9^(xâˆ’1) => 9^1 => m=9

apply the same to
3^(4xâˆ’2) => 3^6 =9*9*9

Now check with the options,
only option that match is C

Regards,
Uva.

Known is a drop Unknown is an Ocean

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theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Tue Dec 24, 2013 10:36 am

m = 9^(x-1) = 9^x/9

3^(4x-2) = 9^x*9^x/9 = m * 9^x ==> m * 9 * m = 9 * m^2
[spoiler]
{C}[/spoiler]

R A H U L

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