Coffee cart

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Coffee cart

by georgepaul0071987 » Sun Oct 30, 2011 7:36 am
A coffee cart made $2400 in revenue . If a large cup of coffee costs twice as much as a small cup , the cart sold 950 large cups and it sold nothing besides the two sizes , then how many small cups of coffee did it sell ?

(1) A large cup of coffee costs $2
(2) If the cart had sold 20% fewer smaller cups , its revenue would have been reduced by 4%

[spoiler] The OA is given as D . But I think the answer should be A . I don't quite understand how statement (2) is sufficient to solve this problem . Because if you take only (2) then you'll have two unknown variables ( the cost of either the large cup/small cup as well as the number of small cups , how can you solve that ? ) [/spoiler]

[/spoiler]
Source: — Data Sufficiency |

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by yasha_gmat » Sun Oct 30, 2011 8:54 am
Below is my explanation as to why 2 is sufficient to answer the question

Given Information
1. Total revenue = 2400$
2. Large cup of coffee costs twice as much as a small cup, CL = 2 * CS
3. Number of Large Cup sold, x = 950

With the given information I can write
2400 = CL * 950 + CS * y --- (1) where y is number of small cup sold
Substituting CL = 2 * CS in (1),
2400 = CS * 1900 + CS * y --- (2)

Statement 2 says,
2304 = CS * 1900 + CS * (4y/5) --- (3)

Subtracting (2) and (3), we get CS * y = 480
Put this value back into (2) or (3) and you will get CS and in turn you can find y (number of small cups)