Target Test Prep 20% Off Flash Sale is on! Code: FLASH20

Redeem
Target Test Prep Flash Sale
Target Test Prep is 20% off right now!
Use code FLASH20

Available with Beat the GMAT members only code

MORE DETAILS
Target Test Prep Flash Sale
Magoosh
Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh

Cars P & Q are approaching each other on the same highwa

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 768
Joined: Wed Dec 28, 2011 4:18 pm
Location: Berkeley, CA
Thanked: 387 times
Followed by:140 members

Cars P & Q are approaching each other on the same highwa

by Mike@Magoosh » Fri Nov 21, 2014 4:15 pm
Cars P & Q are approaching each other on the same highway. Car P is moving at 49 mph northbound and Car P is moving at 61 mph southbound. At 2:00 pm, they are approaching each other and 120 mi apart. Eventually they pass each other. At what clock time are they moving away from each other and 45 miles apart?
(A) 3:06 pm
(B) 3:30 pm
(C) 3:54 pm
(D) 5:21 pm
(E) 6:15 pm


For a set of practice problems on Motion, including the OA & OE for this particular problem, see:
https://magoosh.com/gmat/2014/gmat-pract ... on-motion/

Mike :-)
Magoosh GMAT Instructor
https://gmat.magoosh.com/
Top
Newbie | Next Rank: 10 Posts
Posts: 7
Joined: Tue Jun 24, 2014 4:04 pm

by Chicagosummer » Fri Nov 21, 2014 5:41 pm
The combined speed of the cars is 110 m/ hr
The have to cut a distance of 165 m
It will take 1.5 hours
Hence the time will be 3:30 (B)
Top
Master | Next Rank: 500 Posts
Posts: 447
Joined: Fri Nov 08, 2013 7:25 am
Thanked: 25 times
Followed by:1 members

by Mathsbuddy » Mon Nov 24, 2014 6:32 am
A sketch can help (see graph).
Then using y = mx + c for each car:
Distance between P and Q = pt - (qt + 120) = 45
So, t = (45 + 120)/(p-q) = 165/(49 - -61) = 165/110 = 1.5
Therefore clock time = 2pm + 1.5h = 3.30pm
Attachments
Car Graph.PNG
Top
User avatar
Legendary Member
Posts: 1100
Joined: Sat May 10, 2014 11:34 pm
Location: New Delhi, India
Thanked: 205 times
Followed by:24 members

by GMATinsight » Tue Nov 25, 2014 3:39 am
Nice Graph!!!

But GMAT doesn't allow us leisure of time that we can be that creative.

Relative Distance to be travelled = 120 + 45 = 165 Miles

Relative Speed (Opp.Dir) = 49 + 61 = 110 Miles/Hr

Time = Distance / Speed = 165 / 110 = 1.5 Hour from the state of Journey i.e. they meet at 3:30 PM

Answer: Option B
"GMATinsight"Bhoopendra Singh & Sushma Jha
Most Comprehensive and Affordable Video Course 2000+ CONCEPT Videos and Video Solutions
Whatsapp/Mobile: +91-9999687183 l [email protected]
Contact for One-on-One FREE ONLINE DEMO Class Call/e-mail
Most Efficient and affordable One-On-One Private tutoring fee - US$40-50 per hour
Top
Master | Next Rank: 500 Posts
Posts: 447
Joined: Fri Nov 08, 2013 7:25 am
Thanked: 25 times
Followed by:1 members

by Mathsbuddy » Wed Nov 26, 2014 7:09 am
GMATinsight wrote:Nice Graph!!!

But GMAT doesn't allow us leisure of time that we can be that creative.

Relative Distance to be travelled = 120 + 45 = 165 Miles

Relative Speed (Opp.Dir) = 49 + 61 = 110 Miles/Hr

Time = Distance / Speed = 165 / 110 = 1.5 Hour from the state of Journey i.e. they meet at 3:30 PM

Answer: Option B
Thanks for your response,

True, GMat time is very limited. However, I am offering an alternative method of understanding. With a mental image of the graphs and a comprehension of the equation of a straight line, it is very simple and quick to create the equation given. I like the simplicity of your approach of finding the relative velocity by adding them. Cheers!
Top
Post new topic Post Reply
• Page 1 of 1