Sunday, August 21, 2011

Manhattan GRE's Math Beast Challenge problem for this week

Here it is:

This Week's Problem: "Clement Walks"

Q: Clement walks around an oval-shaped track at a constant rate of 50 seconds per lap. If 18 laps equal a mile, how many miles does Clement walk in 54 minutes?

A:

(A) 2
(B) 2.5
(C) 3
(D) 3.6

This took me about a minute to figure out. It's just quick algebra. The more gifted among you can doubtless do this in your heads. (The answer will be posted later in the comments.)


_

6 comments:

  1. I think 18 laps is 15 minutes, so one mile takes 15 minutes. In 54 minutes, one would walk more than three miles, so I think "D" is the answer.

    And it took me too long to do that in my head . . . a couple of laps worth, I guess.

    Jeffery Hodges

    * * *

    ReplyDelete
  2. Bingo. There are several different approaches one can use, but it sounds as if you used this approach:

    1 lap is done in 5/6 minutes.

    Therefore:

    18 laps are done in 15 minutes. (This can be seen by setting up a proportion.)

    1 mile in 15 minutes = 4mph.

    4 mph for .9 hours (54 minutes) = 3.6 miles.

    QED. (Quirky, erotic, delicious.)

    ReplyDelete
  3. Actually, I just thought, "Hmmm . . . at fifty seconds per lap, six laps takes five minutes, so eighteen laps is fifteen minutes."

    And I took it from there.

    Jeffery Hodges

    * * *

    ReplyDelete
  4. That's probably an easier way to do it.

    ReplyDelete
  5. Since I only had to be close enough to exclude the other answers, I simply looked at 54/18. If it took a minute to do a lap, '3 miles' would be the answer. As the laps were slightly faster, it must be '3.6 miles' or D. I didn't see the need to fine-tune my calculation. Lazy, I guess.

    ReplyDelete
  6. Even faster!

    This problem is so much easier than that damn "spinach rows" problem.

    ReplyDelete

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