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akane: Newbie | Next Rank: 10 Posts; Posts: 8; Joined: Wed Jan 12, 2011 6:00 am

by akane » Sat Nov 05, 2011 8:15 am

Does anyone know a way to solve questions like what is the value of 2^5+2^5+3^5+3^5+3^5 I keep seeing that in the GMAT testprep.I would like to know if there is an (efficient)method for tackling these kind of questions.Thanks for your posts.

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Source: Beat The GMAT — Problem Solving | Sat Nov 05, 2011 8:15 am

vaibhavgupta: Master | Next Rank: 500 Posts; Posts: 416; Joined: Tue Aug 30, 2011 2:18 pmFollowed by: 9 members; Location: Delhi, India; Thanked: 13 times

by vaibhavgupta » Sat Nov 05, 2011 9:25 am

akane wrote:Does anyone know a way to solve questions like what is the value of 2^5+2^5+3^5+3^5+3^5 I keep seeing that in the GMAT testprep.I would like to know if there is an (efficient)method for tackling these kind of questions.Thanks for your posts.

it will come down to 2^6+3^5*2

which = 64+ 486
= 550

could u explain a bit more about wht u want strategies on?

If OA is A, IMO B
If OA is B, IMO C
If OA is C, IMO D
If OA is D, IMO E
If OA is E, IMO A

FML!! :/

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GmatMathPro: GMAT Instructor; Posts: 349; Joined: Wed Sep 28, 2011 3:38 pmFollowed by: 54 members; Location: Austin, TX; Thanked: 236 times; GMAT Score:770

by GmatMathPro » Sat Nov 05, 2011 9:48 am

akane wrote:Does anyone know a way to solve questions like what is the value of 2^5+2^5+3^5+3^5+3^5 I keep seeing that in the GMAT testprep.I would like to know if there is an (efficient)method for tackling these kind of questions.Thanks for your posts.

Let x=2^5, let y=3^5

The expression becomes x+x+y+y+y=2x+3y=2*2^5+3*3^5=

2^6+3^6=64+729=793.

At the end, if you don't know the values of 2^6 or 3^6 off the top of your head, the best you can do is rewrite them: 2^6=(2^3)^2=8^2=64. 3^6=(3^2)^3=9^3=81*9=729.

Depending on the answer choices you may be able to get the answer just based on the unit's digit and not have to calculate it completely.

Pete Ackley
GMAT Math Pro
Free Online Tutoring Trial

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vaibhavgupta: Master | Next Rank: 500 Posts; Posts: 416; Joined: Tue Aug 30, 2011 2:18 pmFollowed by: 9 members; Location: Delhi, India; Thanked: 13 times

by vaibhavgupta » Sat Nov 05, 2011 9:50 am

GmatMathPro wrote:
akane wrote:Does anyone know a way to solve questions like what is the value of 2^5+2^5+3^5+3^5+3^5 I keep seeing that in the GMAT testprep.I would like to know if there is an (efficient)method for tackling these kind of questions.Thanks for your posts.
Let x=2^5, let y=3^5

The expression becomes x+x+y+y+y=2x+3y=2*2^5+3*3^5=

2^6+3^6=64+729=793.

At the end, if you don't know the values of 2^6 or 3^6 off the top of your head, the best you can do is rewrite them: 2^6=(2^3)^2=8^2=64. 3^6=(3^2)^3=9^3=81*9=729.

Think u did a mistake there..

3^5+3^5 is not equal to 3^6
3^5 common (1+1)
2*3^5

If OA is A, IMO B
If OA is B, IMO C
If OA is C, IMO D
If OA is D, IMO E
If OA is E, IMO A

FML!! :/

Like this post

vaibhavgupta: Master | Next Rank: 500 Posts; Posts: 416; Joined: Tue Aug 30, 2011 2:18 pmFollowed by: 9 members; Location: Delhi, India; Thanked: 13 times

by vaibhavgupta » Sat Nov 05, 2011 9:51 am

vaibhavgupta wrote:
GmatMathPro wrote:
akane wrote:Does anyone know a way to solve questions like what is the value of 2^5+2^5+3^5+3^5+3^5 I keep seeing that in the GMAT testprep.I would like to know if there is an (efficient)method for tackling these kind of questions.Thanks for your posts.
Let x=2^5, let y=3^5

The expression becomes x+x+y+y+y=2x+3y=2*2^5+3*3^5=

2^6+3^6=64+729=793.

At the end, if you don't know the values of 2^6 or 3^6 off the top of your head, the best you can do is rewrite them: 2^6=(2^3)^2=8^2=64. 3^6=(3^2)^3=9^3=81*9=729.
Think u did a mistake there..

3^5+3^5 is not equal to 3^6
3^5 common (1+1)
2*3^5

oHh... i did not see there are 3 of them

my bad !:) sorry

If OA is A, IMO B
If OA is B, IMO C
If OA is C, IMO D
If OA is D, IMO E
If OA is E, IMO A

FML!! :/

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