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## Comment on

Multiple Trips or Multiple Travelers## Two trains, X and Y, started

(A) 37.5

(B) 40.0

(C) 60.0

(D) 62.5

(E) 77.5 Don't know what should be done after taking out per hour speed of x and y

## There are some very nice

There are some very nice solutions here: http://www.beatthegmat.com/trains-from-two-opposite-ends-t286355.html

Please let me know if you need any clarification.

## Speed of Train X 20kmph and

So,Train X would travel 20*15/8=37.5 km before meeting Train Y. I don't understand is how it came out to be 15/8 . I understand that we take out speed . After that I am confused

Thanks for help

## Let's take it from 20T + (100

Let's take it from 20T + (100/3)(T) = 100 (where T = the time each train travels until they meet)

Eliminate the fraction by multiplying both sides by 3.

We get: 60T + 100T = 300

Combine: 160T = 300

Solve: T = 300/160 = 30/16 = 15/8

So, each train travels for 15/8 hours

Since train X travels at 20 km per hours, its travel distance = (speed)(time) = (20)(15/8) = 300/8 = 150/4 = 37.5 km

## Jerry and Jim run a race of

A. 8,10

B. 4,5

C. 5,9

D. 6,9

E. 7,10

## You can find my solution here

You can find my solution here: https://gmatclub.com/forum/jerry-and-jim-run-a-race-of-2000-m-first-jerr...

## Hey,

1st off, the Jerry and Jim question still gives me nightmares at night. I straight up hate that question now.

https://gmatclub.com/forum/ann-and-bea-leave-townville-at-the-same-time-and-travel-237882.html

This question however was much more to my liking.

Furthermore, out of a silly mistake I ended up finding a much easier solution.

Upon reading the question I assumed, wrongly, that the 2k distance meant 2000km. Then I assumed a value for Bee's speed, 100kmph, then naturally Anne's speed was 400kmph.

This allowed some easy arithmetic which left me with 800km as an answer; Foolishly now I checked the answer choices and found that K was in fact a variable. So I just multiplied and divided 800 by 1000. (which is 2k without the 2) replaced the numerator 1000 with K, and got 4k/5 .

Though later I realised that a much easier option would've been to see which of the answers gave me an 800 if I replaced the answer K's with 1000.

## The Jim & Jerry question

The Jim & Jerry question (here https://gmatclub.com/forum/jerry-and-jim-run-a-race-of-2000-m-first-jerr...) is a killer. Hopefully, the nightmares will subside soon :-)

As for the Ann & Bea question (here https://gmatclub.com/forum/ann-and-bea-leave-townville-at-the-same-time-...), it never dawned on me (when I created the question) that 2K might be misinterpreted as 2000, but I can totally see it now. That said, the test-makers would never assume that test-takers are aware that we can use "2K" to represent 2000

Once you realized your error, I like how you were able to use your existing calculations to determine the correct answer. Good stuff!

## My quick intuition-based

## Great logic!

Great logic!

## Hi Brent,

The current in a river is 4 mph. A boat can travel 20 mph in still water. How far up the river can the boat travel if the round trip is to take 10 hours?

A. 69 miles

B. 88 miles

C. 96 miles

D. 100 miles

E. 112 miles

My question concerns assigning the “time” variable: When I set up the equation this way,

24(T1) = 16(10−T1)

I am confused as to why (it seems like it should not matter) if you set it up this way

24(10-T) = 16(T1)

As the time is the same - 10 hours! But it does matter and I get a different answer for the Time.

Is there something I am missing? How do you know which time (10 – T or T) to assign to which rate?

## To avoid confusion, it helps

To avoid confusion, it helps to formally assign your variables.

In the equation 24(T1) = 16(10−T1), T1 represents the time spent traveling DOWNSTREAM at 24 miles per hour.

In the equation 24(10-T) = 16(T1), T1 represents the time spent traveling UPSTREAM at 16 miles per hour.

Does that help?

Cheers,

Brent

## Yes! I was under the

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