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 350,000 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:

A man travels 120 miles by ship, 450 by train and 60 by car [#permalink]
21 Dec 2011, 05:33

A man travels 120 miles by ship, 450 by train and 60 by car taking altogether 13 hours and 30 minutes for the entire journey. The speed of the train is 3 times that of the car and 1.5 times that of the ship. Find the speed of the train.

speed of car = x miles/hr speed of ship=2x miles/hr speed of train = 3x miles/hr

soln 1:

Total distance travelled=120+450+60=630 miles Total time = 13.5 or 27/2 hours Total speed = 6x miles per hour

hence 6x *27/2 = 630

x= 70/9 hence speed of train (3x)=70/3 or 23.3

Soln 2 :

Time taken by the train = distance/speed = 450/3x or 150/x ship=120/2x or 60/x car =60/x

since the total time ix 27/2 we can equate them

150/x+60/x+60/x=27/2 270/x=27/2 ---> x = 20

hence speed of train (3x) = 60 m/hr

why am i getting 2 different solns ? which method is wrong and why ..

Last edited by Bunuel on 25 Oct 2013, 08:16, edited 1 time in total.

Re: Rate,distance,time - which method is correct?? [#permalink]
21 Dec 2011, 06:14

Expert's post

rvinodhini wrote:

A man travels 120 miles by ship,450 by train and 60 by car taking altogether 13 hrs 30 min for the entire journey. The speed of the train is 3 times that of the car and 1.5 times that of the ship.Find the speed of the train.

speed of car = x miles/hr speed of ship=2x miles/hr speed of train = 3x miles/hr

soln 1:

Total distance travelled=120+450+60=630 miles Total time = 13.5 or 27/2 hours Total speed = 6x miles per hour

hence 6x *27/2 = 630

x= 70/9 hence speed of train (3x)=70/3 or 23.3

The first solution is the one that's incorrect. I highlighted the mistake in red. You just added the three speeds to find what you've called the 'total speed', and then used it as if it were the average speed. You do not add speeds together to find average speed - for example, If you travel, say, 20 mph by car, then 60 mph by train, your average speed will never be 80 mph. It will be somewhere between 20 and 60 mph. _________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Re: Rate,distance,time - which method is correct?? [#permalink]
21 Dec 2011, 06:23

Quote:

The first solution is the one that's incorrect. I highlighted the mistake in red. You just added the three speeds to find what you've called the 'total speed', and then used it as if it were the average speed. You do not add speeds together to find average speed - for example, If you travel, say, 20 mph by car, then 60 mph by train, your average speed will never be 80 mph. It will be somewhere between 20 and 60 mph.

Re: Rate,distance,time - which method is correct?? [#permalink]
25 Oct 2013, 08:21

1

This post received KUDOS

Expert's post

waltiebikkiebal wrote:

BDSunDevil wrote:

how do you find speed of the ship: 2x? edited: never mind. i got it

Great question.

I still don't get why the speed of the ship is 2x.

Say the speed of the car is x miles per hour.

The speed of the train is 3 times that of the car --> the speed of the train is 3x miles per hour. The speed of the train is 1.5 times that of the ship --> 3x=1.5*(speed of the ship) --> (speed of the ship)=3x/1.5=2x.

Re: Rate,distance,time - which method is correct?? [#permalink]
25 Oct 2013, 08:24

Bunuel wrote:

waltiebikkiebal wrote:

BDSunDevil wrote:

how do you find speed of the ship: 2x? edited: never mind. i got it

Great question.

I still don't get why the speed of the ship is 2x.

Say the speed of the car is x miles per hour.

The speed of the train is 3 times that of the car --> the speed of the train is 3x miles per hour. The speed of the train is 1.5 times that of the ship --> 3x=1.5*(speed of the ship) --> (speed of the ship)=3x/1.5=2x.

Re: A man travels 120 miles by ship, 450 by train and 60 by car [#permalink]
07 Mar 2014, 17:42

Answer is 60? Ratio of speeds is given: T=3x C=x S=2x To calculate:3x or x Total time taken=Total Dist. By resp modes/speed of diff. Modes 13.5=450/3x + 120/2x + 60/x X=60 on simplification

Posted from my mobile device

gmatclubot

Re: A man travels 120 miles by ship, 450 by train and 60 by car
[#permalink]
07 Mar 2014, 17:42

The Stanford interview is an alumni-run interview. You give Stanford your current address and they reach out to alumni in your area to find one that can interview you...

Originally, I was supposed to have an in-person interview for Yale in New Haven, CT. However, as I mentioned in my last post about how to prepare for b-school interviews...

Interested in applying for an MBA? In the fourth and final part of our live QA series with guest expert Chioma Isiadinso, co-founder of consultancy Expartus and former admissions...