Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

01 May 2012, 20:29

1

This post received KUDOS

18

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

74% (03:13) correct
26% (02:29) wrong based on 505 sessions

HideShow timer Statistics

Two boats are heading towards each other at constant speeds of 5 miles/hr and 20 miles/hr respectively. They begin at a distance 20 miles from each other. How far are they (in miles) one minute before they collide ?

Two boats are heading towards each other at constant speeds of 5 miles/hr and 20 miles/hr respectively. They begin at a distance 20 miles from each other. How far are they (in miles) one minute before they collide ?

A. 1/12 B. 5/12 C. 1/6 D. 1/3 E. 1/5

The question asks: how far apart will they be 1 minute=1/60 hours before they collide?

Since the combined rate of the boats is 5+20=25 mph then 1/60 hours before they collide they'll be rate*time=distance --> 25*1/60=5/12 miles apart.

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

02 May 2012, 21:34

Thanks Bunnel for the great link - awesome questions!!

For this one (two boats heading towards each other) - i calculated the time they would collide with each other (48th min) and then "tried" calculating from there on, taking eons to solve - how can the problem be solved with this apporach ? is 25*1/60 the only way to solve such problems ?

Thanks Bunnel for the great link - awesome questions!!

For this one (two boats heading towards each other) - i calculated the time they would collide with each other (48th min) and then "tried" calculating from there on, taking eons to solve - how can the problem be solved with this apporach ? is 25*1/60 the only way to solve such problems ?

It's not the only way but for sure the shortest way to solve this problem.
_________________

Thanks Bunnel for the great link - awesome questions!!

For this one (two boats heading towards each other) - i calculated the time they would collide with each other (48th min) and then "tried" calculating from there on, taking eons to solve - how can the problem be solved with this apporach ? is 25*1/60 the only way to solve such problems ?

Bunuel has already given you a great and most direct approach for this question. But if you did go the round about way, you could have solved it in this way:

Since their combined speed is 20 + 5 = 25 miles/hr, they cover 20 miles in \(\frac{20}{25}\) hrs i.e. \(\frac{20}{25} * 60\) mins = 48 mins

Now, in 48 mins, they cover 20 miles. So in 1 min, they must have covered 20/48 = 5/12 miles
_________________

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

25 Aug 2012, 10:53

1

This post received KUDOS

Hi Bunuel, Your explanation is always the best. I have a slightly different Logic to solve this question. Hope you will like the logic The question asks: How much distance will both travel in 1 minute? Since the combined rate of the boats is 5+20=25 mph = 25/60 mile/min = 5/12 mile/min Hence Answer: B.
_________________

If you like my Question/Explanation or the contribution, Kindly appreciate by pressing KUDOS. Kudos always maximizes GMATCLUB worth-Game Theory

If you have any question regarding my post, kindly pm me or else I won't be able to reply

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

06 Nov 2013, 14:47

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

06 Nov 2013, 18:21

Two boats are heading towards each other at constant speeds of 5 miles/hr and 20 miles/hr respectively. They begin at a distance 20 miles from each other. How far are they (in miles) one minute before they collide?

I probably did this a bit backwards but here is how I figured it out...

The boats travel at a combined rate of 25 miles/hour. If they need to cover 20 miles, it will take them 20/ (5/12) or roughly 48 minutes to reach one another. Either way, one minute before they collide, they will be 5/12ths of a mile away from one another, the distance they travel combined every minute. In this way, it is almost a trick question.

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

19 Nov 2013, 17:38

Bunuel wrote:

gmihir wrote:

Two boats are heading towards each other at constant speeds of 5 miles/hr and 20 miles/hr respectively. They begin at a distance 20 miles from each other. How far are they (in miles) one minute before they collide ?

A. 1/12 B. 5/12 C. 1/6 D. 1/3 E. 1/5

The question asks: how far apart will they be 1 minute=1/60 hours before they collide?

Since the combined rate of the boats is 5+20=25 mph then 1/60 hours before they collide they'll be rate*time=distance --> 25*1/60=5/12 miles apart.

I figured that 5*T+20*T=20 (since they'll have traveled 20 miles combined when they collide). so 25T=20, thus T=4/5. So if they collide at the 48 minute mark, then the distance they travel in 44 minutes combined, subtracted from 20 should give you the answer. so

5*(47/60)+20*(47/60)=D

235/60+940/60=D

1175/60=D

19 \(\frac{35}{60}\)=D

So if they had traveled 19 35/60 miles in 44 minutes combined, then one minute before they collide they should be 25/60 miles apart.

EDIT: Just edited my work. I had a glaring error. My method did work. I keep doing this. I don't know what's happening to me. I'm starting to become concerned. I make errors in calculations on roughtly 80% of the problems I do. I read the questions, and by the second line of the question my mind is already wandering and I don't see or remember anything after the first few words of the question. UGH. Just today I've done ~100 problems, and I made errors in simple addition, or just didn't remember a constraint (answer must be positive or something) on 89 of them. I feel like my brain is dying or something.

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

18 Sep 2014, 05:12

Sorry I don't get it The question states that we must find out the distance 1 min from the time of collision. So if they collided at the 48th minute, question asks us to find the distance of the 2 boats from each other in the 47th minute right?

Sorry I don't get it The question states that we must find out the distance 1 min from the time of collision. So if they collided at the 48th minute, question asks us to find the distance of the 2 boats from each other in the 47th minute right?

Yes, there are two ways we can find the distance between the boats in the 47th minute:

One way is we find the distance traveled by the boats in 47 mins and then subtract that out of the total distance. Another way is to find the distance they will cover in the last 1 min. That must be the distance between them in the 47th minute. Because at the end of the 48th minute, the boats meet - i.e. there is no distance between them. Knowing their speed, we know the distance traveled by them in 1 min and hence know the distance between them 1 min before they meet. The solutions above use this approach to get the answer.
_________________

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

30 Oct 2014, 10:49

1

This post was BOOKMARKED

thank you for the valuable reply but why are we subtracting the total from 20 and not subtracting them by each other(as per my solution), as that will give us how far are they from each other.. confused.

thank you for the valuable reply but why are we subtracting the total from 20 and not subtracting them by each other(as per my solution), as that will give us how far are they from each other.. confused.

In 47 minutes boat 1 covers (16/48)*47 = 47/3 miles and boat 2 covers (4/48) *47 = 47/12 miles. Together in 47 minutes they cover 47/3 + 47/12 = 235/12 miles. Therefore after 47 minutes, so 1 minute before they meet, they will be 20 - 235/12 = 5/12 miles apart.

Re: Two boats are heading towards each other at constant speeds [#permalink]

Show Tags

30 Jan 2015, 05:51

One question,

I thought that when 2 objects are moving towards each other we subtract the rates, as they cover this distance. When they more away from each other we add the rates because they create the distance. In this case, why did we add the rates?

gmatclubot

Re: Two boats are heading towards each other at constant speeds
[#permalink]
30 Jan 2015, 05:51

Happy New Year everyone! Before I get started on this post, and well, restarted on this blog in general, I wanted to mention something. For the past several months...

It’s quickly approaching two years since I last wrote anything on this blog. A lot has happened since then. When I last posted, I had just gotten back from...

Happy 2017! Here is another update, 7 months later. With this pace I might add only one more post before the end of the GSB! However, I promised that...