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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

speed

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 162
Joined: Mon Jul 28, 2008 8:33 pm
Location: San Jose,CA
Thanked: 1 times
by ddm » Mon Sep 08, 2008 1:39 pm
A and B ran a race of 480 m. In the first heat, A gives B a head start of 48 m and beats him by 1/10 th of a minute. In the second heat, A gives B a head start of 144 m and is beaten by 1/30 th of a minute. What is B’s speed in m/s?

(A) 12

(B) 14

(C) 16

(D) 18

(E) 20
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pmFollowed by: 3 members
Location: INDIA
Thanked: 84 times

Re: speed

by sudhir3127 » Mon Sep 08, 2008 8:59 pm
ddm wrote:A and B ran a race of 480 m. In the first heat, A gives B a head start of 48 m and beats him by 1/10 th of a minute. In the second heat, A gives B a head start of 144 m and is beaten by 1/30 th of a minute. What is B’s speed in m/s?

(A) 12

(B) 14

(C) 16

(D) 18

(E) 20
Its A 12

1 race:
A runs 480 m in t seconds
B 0.9 x 480 m in t+6 seconds ...............................................1

2nd race:
A runs 480 m in t seconds
B runs 0.7 x 480 m in t-2 seconds .........................................2

Speeds of the runners are constant in both the races

Equate 1 and 2

0.9*480 / (t+6) = 0.7*480 / (t-2)

solve for T

t = 30

substitute the value of t in equation 1

0.9* 480/( 30+6) = 12.

Hope its clear
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Sun Aug 10, 2008 7:38 am

by aditya.gopal » Mon Sep 08, 2008 10:05 pm
Can you please explain how you got the 0.9 and 0.7

thanks!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Sun Aug 10, 2008 7:38 am

by aditya.gopal » Mon Sep 08, 2008 10:06 pm
I figured it out....don't worry
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Mon Oct 01, 2007 9:11 am
Thanked: 2 times

by chykie » Tue Sep 09, 2008 4:28 am
I'm sorry i don't get it, how did you get 0.9 and 0.7?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pmFollowed by: 3 members
Location: INDIA
Thanked: 84 times

by sudhir3127 » Tue Sep 09, 2008 4:54 am
chykie wrote:I'm sorry i don't get it, how did you get 0.9 and 0.7?
in the first race A gives B a head start of 48 m which is 10% ( 48/480)
thus b has to cover the remaining distance only which is 90% of 480m.

similarly 0.7 . B is 144 mts ahead which is 30% ( 144/480) . thus have 2 cover only 70% of the total distance hence 0.7

hope its clear now...

do let me know if u have any doubts..
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 891
Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member
Thanked: 27 times
GMAT Score:660(

Re: speed

by 4meonly » Mon Dec 22, 2008 1:00 am
sudhir3127 wrote: 1 race:
A runs 480 m in t seconds
B 0.9 x 480 m in t+6 seconds ...............................................1

2nd race:
A runs 480 m in t seconds
B runs 0.7 x 480 m in t-2 seconds .........................................2
Guys, please, help me to understand why it was concluded that in each race time was equal?

I got following:
1 race:
A runs 480 m in t(1) seconds
B 0.9 x 480 m in t(1)+6 seconds ...............................................1

2nd race:
A runs 480 m in t(2) seconds
B runs 0.7 x 480 m in t(2)-2 seconds .........................................2
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 546
Joined: Sun Nov 16, 2008 11:00 pm
Location: New Delhi , India
Thanked: 13 times

by ronniecoleman » Mon Dec 22, 2008 1:11 am
A and B ran a race of 480 m. In the first heat, A gives B a head start of 48 m and beats him by 1/10 th of a minute. In the second heat,
A gives B a head start of 144 m and is beaten by 1/30 th of a minute. What is B's speed in m/s?

(A) 12

(B) 14

(C) 16

(D) 18

(E) 20


equation 1: 480-48 / Sb - 480/ Sa = 6
480/Sa - 480-144/Sb = 2


solve both to get Sb as 12
Admission champion, Hauz khaz
011-27565856
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 891
Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member
Thanked: 27 times
GMAT Score:660(

by 4meonly » Mon Dec 22, 2008 1:25 am
I solved this problem in my way. Very long but clear (i think) :)

A and B ran a race of 480 m.
S=480

In the first heat, A gives B a head start of 48 m and beats him by 1/10th of a minute.
B starts 48 m ahead A. But A will be the firast at the finish. B needs additional 1/10th of a minute (6 sec) to get to the finish. Time of A and B are equal here.
So, we got 2 equations using the distance formula:
Racer A: 480 m in t1 seconds => speed of racer A = 480/t1 m/s
Racer B: (480-48) m in t1+6 seconds => speed of racer B = (480-48)/t1+6 = 432/t1+6 m/s


In the second heat, A gives B a head start of 144 m and is beaten by 1/30th of a minute. What is B’s speed in m/s?
So, again we got 2 equations using the distance formula:
Racer A: 480 m in t2+2 seconds => speed of racer A = 480/t2+2 m/s
Racer B: (480-144) m in t2 seconds => speed of racer B = 336/t2 m/s

Speed of each racer are constant, thus:
speed of racer A = 480/t1 = 480/t2+2
speed of racer B = 432/t1+6 = 336/t2

From 480/t1 = 480/t2+2 we have:
1/t1 = 1/t2+2 (divided by 480)
t1=t2+2
substitute this equation to 432/t1+6 = 336/t2
432/t2+8 = 336/t2
solve to get t2 = 28

substitute t2 = 28 in
speed of racer B = 336/t2 m/s
speed of racer B = 12 m/s

Answer A
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 891
Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member
Thanked: 27 times
GMAT Score:660(

by 4meonly » Mon Dec 22, 2008 1:27 am
ronniecoleman wrote:
equation 1: 480-48 / Sb - 480/ Sa = 6
480/Sa - 480-144/Sb = 2


solve both to get Sb as 12
Yes, this reasoning is more clear than my :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 546
Joined: Sun Nov 16, 2008 11:00 pm
Location: New Delhi , India
Thanked: 13 times

by ronniecoleman » Mon Dec 22, 2008 1:48 am
4meonly wrote:
ronniecoleman wrote:
equation 1: 480-48 / Sb - 480/ Sa = 6
480/Sa - 480-144/Sb = 2


solve both to get Sb as 12
Yes, this reasoning is more clear than my :)
Great work ! :D
Admission champion, Hauz khaz
011-27565856
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Thu Oct 23, 2008 9:20 am

by tritrantran » Mon Dec 22, 2008 2:21 am
I'm trying to solve it another way, but I don't know if it works. Can someone else tell me if this is valid...

1st heat:

delta time = 6 sec

delta distance = 48 m

T = D/(Sb-Sa)

6 = 48/(Sb-Sa) valid equation?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 35
Joined: Wed Oct 29, 2008 5:14 am

Re: speed

by coffee5251 » Mon Dec 22, 2008 7:41 am
sudhir3127 wrote:
ddm wrote:
Equate 1 and 2

0.9*480 / (t+6) = 0.7*480 / (t-2)

solve for T

Can you explain why you would set the two equations equal to each other in order to solve for T?

Thanks!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1