BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

circular race

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 81
Joined: Thu Jun 12, 2008 1:57 pm
Thanked: 1 times

circular race

by nikhilagrawal » Wed Jul 23, 2008 4:18 am
A, B and C run around a circular track of length 750m at speeds of 3 m/sec, 6 m/sec and 18 m/sec respectively. If all three start from the same point, simultaneously and run in the same direction, when will they meet for the first time after they start the race?

A. 750 seconds
B. 50 seconds
C. 250 seconds
D. 375 seconds
E. 75 seconds
Top
Source: — Problem Solving |
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pm
Location: INDIA
Thanked: 84 times
Followed by:3 members

by sudhir3127 » Wed Jul 23, 2008 4:27 am
My Answer is 250

When two people are running in the same direction the relative speed is a difference in speeds of the two people.

In this case A=3 B=6 C=18

So relative speed of B wrt A is 6-3 = 3m/s
Relative speed of A wrt to C is 18-3 =15m/s

Therefore relative distances will be:
B wrt A is 750/3 =250
C wrt to A 750/15 = 50

LCM of 250 and 50 is 250 .

theres another method as well..

A takes 250seconds to colplete on round.( 750/3)

B takes 125

C takes 41.67

Hence A= 2B
B=3C

So after 250 lapse a would have completed 1 round B 2 and C 6.

hence 250
Top
Legendary Member
Posts: 1153
Joined: Wed Jun 20, 2007 6:21 am
Thanked: 146 times
Followed by:2 members

Re: circular race

by parallel_chase » Wed Jul 23, 2008 5:31 am
nikhilagrawal wrote:A, B and C run around a circular track of length 750m at speeds of 3 m/sec, 6 m/sec and 18 m/sec respectively. If all three start from the same point, simultaneously and run in the same direction, when will they meet for the first time after they start the race?

A. 750 seconds
B. 50 seconds
C. 250 seconds
D. 375 seconds
E. 75 seconds
Even I got 250 seconds.
Used the LCM method, its faster and better since you can always check your answer if its correct or not.
Top
Post new topic Post Reply
• Page 1 of 1