Riddle (11/15/2007)

deek · Post by **deek** » Thu Nov 15, 2007 11:52 am

A man is walking down a street along which runs a streetcar line. He notices that, for every 40 streetcars which pass him traveling in the same direction as he, 60 pass in the opposite direction. If the man's walking speed is 3 miles per hour, what is the average speed of the streetcars?

The answer is: 15mph

jschall84 · Post by **jschall84** » Thu Nov 15, 2007 12:17 pm

i mean seriously, he just happens to "notice"? who is this guy? THE RAINMAN?@! i refuse to even think about this riddle due to the fact that the scenario in question would never happen!!!.....and its hard...lol

G Fresh · Post by **G Fresh** » Thu Nov 15, 2007 12:23 pm

I don't know that I would consider this a riddle so much as a story problem. Are you covertly trying to make us learn stuff? Not cool man, not cool, but thanks for reminding me yet again of why I'm glad I'm not in high school anymore.

deek · Post by **deek** » Thu Nov 15, 2007 12:33 pm

Sometimes they will be math related, sometimes word puzzles or word plays...they are all there to make you think though. I didn't want to do all of the same kinds, because different people like different types of problems.

But yeah, this is more of a math story problem, but its not that hard...I don't think I'm going to be posting anything that is above middle/high school level...unless it is a trick question, which I will sneak those in as well:)

Krieves · Post by **Krieves** » Thu Nov 15, 2007 1:19 pm

1280 miles an hour.

deek · Post by **deek** » Thu Nov 15, 2007 1:47 pm

Answers should be PM'd to me, not posted in the thread. Thanks!

jschall84 · Post by **jschall84** » Thu Nov 15, 2007 1:58 pm

1.21 jiggawatts?

deek · Post by **deek** » Thu Nov 15, 2007 2:07 pm

This must either be a tougher one for the board or not enough people have looked it over. The last two I posted had 3 to 5 PMs each and all of them with correct answers...interesting!

MrSpall · Post by **MrSpall** » Thu Nov 15, 2007 4:34 pm

Just started looking it over, will have the answer soon.

For the record - I love math.

Garr · Post by **Garr** » Thu Nov 15, 2007 5:18 pm

I haven't had time to work it out yet. I don't even know where to begin though.

Well, I'm off to get the munchkin from pre-school. Yay for kids!

deek · Post by **deek** » Thu Nov 15, 2007 5:57 pm

This seems to be the toughest one so far, as I have only gotten one correct answer. If you need a hint, highlight the rest of this sentence --> 50 mph is NOT the correct answer

deek · Post by **deek** » Fri Nov 16, 2007 5:51 pm

Only two correct answers...its posted now, but if you are still working on it, don't look and send me a PM.

I'll post a new on on Monday.

Krieves · Post by **Krieves** » Fri Nov 16, 2007 6:22 pm

I was really close.

=^-..-^= · Post by **=^-..-^=** » Tue Nov 20, 2007 11:18 pm

Okay where did I go wrong on this?

He is walking 1/3 as fast as the streetcars, because the number of streetcars passing him is reduced by a third: 40/60

So, wouldn't the formula be 1/3(X) = 3mph or 9mph?

MrSpall · Post by **MrSpall** » Wed Nov 21, 2007 8:16 am

HERE IS HOW THE ANSWER IS DETERMINED! SPOLIER ALERT!

Actually you'd be better served going with a pair of comparative fractions.

The speed of the trains becomes the variable x. The relative speed of the trains going towards him is increased by 3 (x+3) while the speed of the trains he's walking alongside would be relatively decreased by three (x-3).

Set your comparison up as follows:
x-3/x+3=40/60
Simplified:
x-3/x+3=2/3
Cross multiply:
3(x-3)=2(x+3)
Work it out algebraically from there:
3x-9=2x+6
x-9=6
x=15