NEW HERE? LEARN MORE
closeclose
Last visit was: 27 Apr 2024, 21:09 It is currently 27 Apr 2024, 21:09
Decision Tracker
My Rewards
New posts
New comers' posts

Close
GMAT Club Daily Prep
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A man travels 120 miles by ship, 450 by train and 60 by car

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
rvinodhini
Intern
Intern
Joined: 05 Aug 2011
Posts: 16
Own Kudos [?]: 34 [7]
Given Kudos: 64
Send PM
Reviews Badge
A man travels 120 miles by ship, 450 by train and 60 by car [#permalink] New post   Updated on: 25 Oct 2013, 09:16
2
Kudos
5
Bookmarks
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 ..

Originally posted by rvinodhini on 21 Dec 2011, 06:33.
Last edited by Bunuel on 25 Oct 2013, 09:16, edited 1 time in total.
RENAMED THE TOPIC.
User avatar
L
IanStewart
GMAT Tutor
Joined: 24 Jun 2008
Posts: 4128
Own Kudos [?]: 9247 [1]
Given Kudos: 91
 Q51  V47
Send PM
Re: Rate,distance,time - which method is correct?? [#permalink] New post   21 Dec 2011, 07:14
1
Kudos
Expert Reply
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.
User avatar
rvinodhini
Intern
Intern
Joined: 05 Aug 2011
Posts: 16
Own Kudos [?]: 34 [0]
Given Kudos: 64
Send PM
Reviews Badge
Re: Rate,distance,time - which method is correct?? [#permalink] New post   21 Dec 2011, 07:23
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.



Oops ..I get it know ... Thanks Stewart

lesson learnt ...NEVER ADD SPEEDS...
User avatar
BDSunDevil
Manager
Manager
Joined: 13 May 2011
Posts: 144
Own Kudos [?]: 509 [0]
Given Kudos: 11
Concentration: Supply Chain, Logistics
WE 1: IT 1 Yr
WE 2: Supply Chain 5 Yrs
Send PM
Re: Rate,distance,time - which method is correct?? [#permalink] New post   21 Dec 2011, 07:31
how do you find speed of the ship: 2x?
edited: never mind. i got it
avatar
waltiebikkiebal
Intern
Intern
Joined: 14 Feb 2012
Posts: 16
Own Kudos [?]: 17 [0]
Given Kudos: 6
Send PM
Re: Rate,distance,time - which method is correct?? [#permalink] New post   25 Oct 2013, 09:02
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.
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92959
Own Kudos [?]: 619506 [2]
Given Kudos: 81611
Send PM
CAT Tests Forum Quiz Mode
Re: Rate,distance,time - which method is correct?? [#permalink] New post   25 Oct 2013, 09:21
2
Kudos
Expert Reply
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.

Hope it's clear.
avatar
waltiebikkiebal
Intern
Intern
Joined: 14 Feb 2012
Posts: 16
Own Kudos [?]: 17 [0]
Given Kudos: 6
Send PM
Re: Rate,distance,time - which method is correct?? [#permalink] New post   25 Oct 2013, 09:24
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.

Hope it's clear.


Yeah, ofc.

Now it makes sense!

Thank you.
avatar
PareshGmat
SVP
SVP
Joined: 27 Dec 2012
Status:The Best Or Nothing
Posts: 1562
Own Kudos [?]: 7209 [3]
Given Kudos: 193
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Send PM
Re: A man travels 120 miles by ship, 450 by train and 60 by car [#permalink] New post   07 Mar 2014, 00:36
2
Kudos
1
Bookmarks
Answer = 60 Miles/hr

\(\frac{120}{2x} + \frac{450}{3x} + \frac{60}{x} = 13.5\)

Solving this, 3x = 60 = Speed of train.

Please refer diagram below:
Attachments

se.jpg
se.jpg [ 16.12 KiB | Viewed 23678 times ]

avatar
B
AKG1593
Manager
Manager
Joined: 20 Dec 2013
Posts: 183
Own Kudos [?]: 290 [0]
Given Kudos: 35
Location: India
Send PM
Re: A man travels 120 miles by ship, 450 by train and 60 by car [#permalink] New post   07 Mar 2014, 18:42
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
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32715
Own Kudos [?]: 822 [0]
Given Kudos: 0
Send PM
Re: A man travels 120 miles by ship, 450 by train and 60 by car [#permalink] New post   30 Jun 2023, 07:30
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.
GMAT Club Bot
gmatclubot
Re: A man travels 120 miles by ship, 450 by train and 60 by car [#permalink]
30 Jun 2023, 07:30
Moderators:
Bunuel
Math Expert
92959 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions