2008 AMC 10B Problem 8

Below is the professionally curated solution for Problem 8 of the 2008 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2008 AMC 10B solutions, or check the answer key.

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Concepts:Diophantine Equationparity

Difficulty rating: 1080

8.

A class collects $50\$50 to buy flowers for a classmate who is in the hospital. Roses cost $3\$3 each, and carnations cost $2\$2 each. No other flowers are to be used. How many different bouquets could be purchased for exactly $50?\$50?

11

77

99

1616

1717

Solution:

If rr roses and cc carnations are bought, then 3r+2c=50.3r+2c=50. Because 2c2c and 5050 are even, 3r3r must be even, so rr is even.

Also 3r50,3r\le 50, so r16.r\le 16. The even values r=0,2,4,,16r=0,2,4,\ldots,16 each give a valid c,c, which is 99 bouquets.

Thus, the correct answer is C.

Problem 8 in Other Years