GMAT Prep

[aosh]

Q - At a certain shop, 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

Answer is D, I get statement 1 but I can't make anything out of statement 2?

[givemeanid]

Dogs = Birds + 20
x/3 = x/5 + 20
x/3 - x/5 = 20
x = 150
You can calculate number of dogs = 150/3 = 50

[induscrede]

statement two is sufficeint cos you know the fraction of dogs - fraction of birds will give you the number 20 so you can calculate all the pets based on that... so its suffice (Don't have to actually find the number)

[MercedesMW]

Thank you so much for asking this question. I have literally spent an hour attempting to figure out this question, and then I said to myself, "Beat the GMAT!" So I looked it up and here you are. Thanks - so nice to feel like part of a community here!