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Word Problem

by carllecat » Tue Nov 17, 2009 8:59 am
At a certain petshop, 1/3 of the pets are dogs and 1/5 of the pets are birds. How many of the pets are dogs?

1) There are 30 birds at the pet shop.

2) There are 20 more dogs than birds at the pet shop.

I know that choice 1 is good, but how about choice 2 and why?
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Source: — Data Sufficiency |
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by Lance123 » Tue Nov 17, 2009 9:41 am
I'm willing to take a stab at Statement 2.

P- All Pets

B- Birds

D- Dogs

1/3P= D

1/5P= B
............................................
From Statement 2
B + 20 = D
=> 1/5P +20 = 1/3P
1/3P- 1/5P= 20
2/15P= 20
P=150 (all pets)

From this it is sufficient to calculate Dogs
2 is sufficient
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by carllecat » Tue Nov 17, 2009 10:38 am
Lance123 wrote:I'm willing to take a stab at Statement 2.

P- All Pets

B- Birds

D- Dogs

1/3P= D

1/5P= B
............................................
From Statement 2
B + 20 = D
=> 1/5P +20 = 1/3P
1/3P- 1/5P= 20
2/15P= 20
P=150 (all pets)

From this it is sufficient to calculate Dogs
2 is sufficient
Thanks Lance!
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