gmatpup wrote:Can someone please give me a quick way to do this question:
A certain store sells all maps at one price and all books at another price. On Monday the store sold 12 maps and 10 books for a total of $38, and on Tuesday the store sold 20 maps and 15 books for a total of $60. At this store, how much less does a map sell for than a book?
A. $0.25
B. $0.50
C. $0.75
D. $1.00
E. $1.25
Answer is B
Here is an alternate approach:
12M + 10B = 38.
Thus, if we buy 6 more maps and 5 more books -- increasing each number by half -- the total cost will increase by half ($19):
18M + 15B = 57.
The second given equation -- 20M + 15B = 60 -- is almost identical to the equation above, but it includes 2 additional maps and a cost increase of $3.
Thus, the 2 additional maps must account for the cost increase:
2M = 3
M = 1.5.
Substituting M=1.5 into the second given equation:.
20(1.5) + 15B = 60.
B = 2.
Thus, B-M = 2-1.5 = .5.
The correct answer is
B.
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