Hi leihannie07,

We're told that over the weekend, a shoe store sold 1/3 of the shoes in its stock and that the average price of the shoes sold was $60 per pair. We're asked for the total revenue from shoe sales over the weekend for this shoe store.

1) When the store closed on Sunday night, 600 pairs of shoes were still in stock.

Fact 1 tells us the number of pairs of shoes that were 'left over' after 1/3 of the pairs of shoes had been sold. Thus, the 600 pairs represents 2/3 of the total shoes.
600 = (2/3)(Total pairs)
900 = Total pairs
900 - 600 = 300 pairs sold, so the total revenue was (300)($60) = $18,000
Fact 1 is SUFFICIENT

2) The store began the weekend with 900 pairs of shoes.

With 900 total pairs, we know that (1/3)(900) = 300 pairs were sold,so the total revenue was (300)($60) = $18,000
Fact 2 is SUFFICIENT

Final Answer: D

GMAT assassins aren't born, they're made,
Rich