og 133 number properties

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mepinoargote: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Wed Apr 28, 2010 12:11 pm

og 133 number properties

by mepinoargote » Fri Aug 27, 2010 6:37 pm

Are all the numbers in a certain list of 15 numbers equal?
(1) The sum of all the numbers in the list is 60
(2) The sum of any 3 numbers in the list is 12

Statement one is easy to evaluate, but what approach should i take with (2)?? The official guide answer is way too long and confusing, please help!

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Source: Beat The GMAT — Data Sufficiency | Fri Aug 27, 2010 6:37 pm

mepinoargote: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Wed Apr 28, 2010 12:11 pm

by mepinoargote » Fri Aug 27, 2010 7:10 pm

Thanks for your help!!!

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pradeepkaushal9518: Legendary Member; Posts: 1309; Joined: Wed Mar 17, 2010 11:41 pm; Thanked: 33 times; Followed by:5 members

by pradeepkaushal9518 » Fri Aug 27, 2010 7:11 pm

all numbers are equal in the list of 15 numbers

1.usm of all number is 60

suppose no is x so x+x+.......15 times = 15x=60
x= 4
sufficients

2.sum of any 3 number is 12

suppose each no is x so sum of any 3 nos will be x+x+x=3x so given that 3x=12 x= 4

sufficient

imo D

A SMALL TOWN GUY

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 am; Thanked: 32 times; Followed by:3 members

by Gurpinder » Fri Aug 27, 2010 7:12 pm

mepinoargote wrote:Are all the numbers in a certain list of 15 numbers equal?
(1) The sum of all the numbers in the list is 60
(2) The sum of any 3 numbers in the list is 12

Statement one is easy to evaluate, but what approach should i take with (2)?? The official guide answer is way too long and confusing, please help!

They keyword for statement 2 is that ANY 3 numbers = 12

All numbers in the list can = 4. How? Because Avg*15=60 --> 4

so 4,4,4,4,4,4,4,4.....

if you change the 4 into any other number, you cannot get 12

So all the numbers must be equal. SUFFICIENT.

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 am; Thanked: 32 times; Followed by:3 members

by Gurpinder » Fri Aug 27, 2010 7:15 pm

pradeepkaushal9518 wrote:all numbers are equal in the list of 15 numbers

1.usm of all number is 60

suppose no is x so x+x+.......15 times = 15x=60
x= 4
sufficients

2.sum of any 3 number is 12

suppose each no is x so sum of any 3 nos will be x+x+x=3x so given that 3x=12 x= 4

sufficient

imo D

No buddy! The answer is (B).

Stmt 1:

Your right! We can get all 4's.

But we can get different numbers as well which will give you a 60 sum. But they wont be equal.

for example 1,1,1,1,1,1,1,1,1,1,1,1,1,1,46.... = 60 but all the numbers are not the same!

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.