Some of you know that I work at Sylvan. One of the programs I teach is an ACT math/science prep class. Normally I can explain the math quite well, but for some reason I came across a problem tonight that I couldn't solve right away! (Now that I've figured it out, it's really not that hard, but for some reason it stumped me.) It bugged me enough that I had to copy it and bring it home, where I worked it out and made Mike show me another way to solve it.
So, here's your big chance. I'm going to put the problem here. Post your answer and how you got that solution, and I'll come back with my explanation later! The only rule is be honest - try to work it out BEFORE you look at the comments section for everyone else's ideas! (Eric B., you are banned from posting until at least 5 other people have taken a shot. Otherwise, everyone else will just look at your answer.)
Here's the problem: "In a downhill ski race, Margo posted a time of 2 minutes and 24 seconds for a course 1.2 miles long. About how many miles per hour did she average for the race?"
Have fun!
6 comments:
is it a trick question? Too obvious? 30 miles per hour is my answer which I got by doing this:
1.2 divided by 2.4 which I multiply by 60
There's probably an easier way but that is my way of finding out unles I am TOTALLY wrong!
I got 30 too.
And this is how:
1.2 miles/(144/3600)
There are 144 seconds in the total trip and 3600 seconds in an hour.
Okay, I'm not sure how to explain this, but I think I have an answer. 2 min and 24 sec is 144 seconds. So, with the info you have, it's 1.2miles/144 sec. Well, you want miles/hour instead. So, 144sec/60sec (to convert to minutes) is 2.4 minutes. 2.4min/60 min (to convert to hours) is .04 hr. So, now you can plug into the problem with miles and hours... 1.2miles/.04 hours - which gives an average of 30 mph.
All right, so you're all smarter than I am. I had to do the 144/3600 and got 0.04. Then I had to do the 1.2/0.04, and I also got 30 mph. Like I said, it wasn't that hard, but it did take me a minute!
Eric, you're now allowed to post.
OK - five people have commented now!
2m24s for 1.2 miles. Those aren't very round numbers, are they. But wait - 10% of a minute is 6 seconds, so 20% of a minute is 12 seconds, and 20% of 2 minutes is 24 seconds. The problem is identical to saying:
2 minutes for 1 mile. And that's easy - 2*30 = 1 hour, so she's averaging 30mph.
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