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A Better Mousetrap (Posted on 2004-01-20) Difficulty: 4 of 5
The following question was asked on a math test:
If 6 cats kill 6 rats in 6 minutes, how many will be needed to kill 100 rats in 50 minutes?

Ryan answered 12, Stefanie said 13, and Tom put down 14 for his answer. After looking at their work, the teacher decided to give all three students credit.

What were the arguments that each student made?

See The Solution Submitted by DJ    
Rating: 4.1818 (11 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: 2/3 of an answer | Comment 5 of 12 |
(In reply to 2/3 of an answer by Charlie)

I don't know about the "teaming up", but 12 is the straight mathematical answer: each cat kills 8 1/3 rats (whatever killing 1/3 of a rat means....)

13 also makes sense: Stefanie reasoned that killing 1/3 of a rat makes no sense at all. So 12 cats couldn't do it in 50 minutes, there would be 4 rats left over, and another cat is needed. I suppose that it takes a few minutes to CATCH the rat first, then time to kill it, and 2 minutes just isn't enough time to do anything.

But I'm also stumped on 14....
  Posted by Brian Wainscott on 2004-01-20 12:34:50

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