A bullet train leaves Kyoto for Tokyo trav....

[steilbergauf]

Hi MGMAT,

first of all I wanted to thank you very much for this forum and the possibility to ask questions!

I have a question regarding distance problems:
Thanks to the strategy guide and the videos of ron on vimeo I have no struggle to set up charts, make up a variable etc. My problem starts when I have to set up an equation.

For example, when I read Q14 in the rates & work problem set (4th edition) I know how to get all the things I need:

A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

(A)12:40 pm (B) 12:49 pm (C) 12:55 pm (0) 1:00 pm (E) 1:05 pm

Insert hard facts, make up a variable and express the other t, d or r in terms of that variable and take the leftovers to set up an equation. My problem is that I sometimes dont know how I have to express this relationship. In Q14 I resulted with the expression 240(t+1/6) and 160t, but I did not know wheter I should set both equal or in relation to 300.

Same for Q15.

Nicky and Cristina are running a 1,000 meter race. Since Cristina is faster than Nicky,
she gives him a 12 second head start. If Cristina runs at a pace of 5 meters per second and Nicky runs at a pace of only 3 meters per second, how many seconds will Nicky have run before Cristina catches up to him?

(A) 15 seconds (B) 18 seconds (C) 25 seconds (0) 30 seconds (E) 45 seconds


When I was left with 5t and 3(t+12) I could notfigure out how I get the relationship (should I set them equal, do I need the 1000m distance or should I even add the distance?).

How can I improve my approach? Does it work when I keep in mind the scenarios à la: hey, that is a kiss scenario so i have to add the distance and bring it in relation two the stuff I just made up with the information?!

Many thanks in advance!

[RonPurewal]

Hi,

* Please read the forum rules (posted at the top of every folder, including this one).

* Please post the complete problems you're discussing. If there are answer choices, post all of the answer choices as well.

Thanks.

[steilbergauf]

Hope its better.

[RonPurewal]

A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

(A)12:40 pm (B) 12:49 pm (C) 12:55 pm (0) 1:00 pm (E) 1:05 pm

Insert hard facts, make up a variable and express the other t, d or r in terms of that variable and take the leftovers to set up an equation. My problem is that I sometimes dont know how I have to express this relationship. In Q14 I resulted with the expression 240(t+1/6) and 160t, but I did not know wheter I should set both equal or in relation to 300.

You just have to think about what's happening in the problem.

Those two expressions represent distances. So, the question is, What's going on with the two distances?

The trains meet in the middle of a 300-mile pathway. So the distances have to add to 300 miles.

[RonPurewal]

Nicky and Cristina are running a 1,000 meter race. Since Cristina is faster than Nicky,
she gives him a 12 second head start. If Cristina runs at a pace of 5 meters per second and Nicky runs at a pace of only 3 meters per second, how many seconds will Nicky have run before Cristina catches up to him?

(A) 15 seconds (B) 18 seconds (C) 25 seconds (0) 30 seconds (E) 45 seconds


When I was left with 5t and 3(t+12) I could notfigure out how I get the relationship (should I set them equal, do I need the 1000m distance or should I even add the distance?).

Again, just think about what's happening.

The 5t and 3(t + 12) represent distances again. What has to be true about the distances?

The way you've set up the problem, the distances should be the same, since they're both distances from the starting point to the point where the two runners meet. (One takes less time, but that's immaterial.)

--

You can also set it up differently.
Another way is to consider that Nicky runs 36 meters in those 12 seconds during which Cristina isn't running yet. So, set the problem up from that point -- i.e., only considering the times during which both runners are running.

In that case, the distances are 3t and 5t, and one distance is 36 meters longer than the other one.

[RonPurewal]

How can I improve my approach? Does it work when I keep in mind the scenarios à la: hey, that is a kiss scenario so i have to add the distance and bring it in relation two the stuff I just made up with the information?!

It doesn't make sense to memorize those scenarios -- it's much easier just to think about them. ("Kiss scenario" is too abstract for me, at least; there's no way I could remember it as such. It's easier just to look at the scenario and say, "Hmm, together they cover 300 miles.")

Those scenarios are presented as illustrations of what you might see.
So, you should think through them, and make sure that your thought process gives results that agree with what's given.
The point, though, is the thought process, not the particular scenarios.