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 →

Lead in a race

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 156
Joined: Sun Jul 15, 2012 12:03 pmFollowed by: 1 member
Location: New York, USA
Thanked: 34 times
by kartikshah » Fri Jul 27, 2012 6:05 pm
In a 100m race, Sam beats John by 4 seconds. On the contrary, if Sam allowed John to start 16m ahead of Sam, then Sam and John reach the finishing point at the same time. How long does Sam take to run the 100m race?

A. 4 seconds

B. 25 seconds

C. 29 seconds

D. 21 seconds

E. 6.25 seconds


Please help with this question.

I don't understand complex RTD questions. Is there a simpler approach to them? I know how to solve the following types with ease:

(a) Simple RTD
(b) Two objects in same direction (time taken to catch up questions)
(c) Two objects in opposite direction (distance apart questions)

But not those questions like the one above!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 342
Joined: Wed Jul 08, 2009 8:50 amFollowed by: 19 members
Thanked: 214 times
GMAT Score:740

by Birottam Dutta » Fri Jul 27, 2012 6:27 pm
See,

When Sam allows for a 16 m head start he and john reach at the same time, so Sam requires the 4 seconds to cover this additional 16m.

Hence, speed of Sam = 16/4 = 4 m/s.

Therefore, time taken by Sam to run the 100m race = 100/4 = 25 seconds.

Answer = B!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 156
Joined: Sun Jul 15, 2012 12:03 pmFollowed by: 1 member
Location: New York, USA
Thanked: 34 times

by kartikshah » Fri Jul 27, 2012 6:30 pm
Huh!
It was this simple?!!
I really need to shed my prejudice for RTD problems :-)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 15
Joined: Wed Jun 06, 2012 9:53 am
Thanked: 1 times

by optimist » Sat Jul 28, 2012 10:57 am
I am getting 21 (C) as the answer, please see if am doing anything wrong

Let time taken by Sam to cover 100m be 't' ==> Sam's speed = 100/t
therefore, time taken by John = t+4 ==> John's speed = 100/(t+4)

Now, since John starts 16 m ahead of Sam,
time taken by Sam to cover 100m = time taken by John to cover 84m:

==> 100/100*t = 84*(t+4)/100
on solving, t = 21

please help
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 520
Joined: Sat Apr 28, 2012 9:12 pmFollowed by: 49 members
Thanked: 339 times
GMAT Score:770

by eagleeye » Sat Jul 28, 2012 11:17 am
optimist wrote:I am getting 21 (C) as the answer, please see if am doing anything wrong

Let time taken by Sam to cover 100m be 't' ==> Sam's speed = 100/t
therefore, time taken by John = t+4 ==> John's speed = 100/(t+4)

Now, since John starts 16 m ahead of Sam,
time taken by Sam to cover 100m = time taken by John to cover 84m:

==> 100/100*t = 84*(t+4)/100
on solving, t = 21

please help
Optimist you are right. The correct answer is D.

John covers the additional 16m in 4s. John's speed = 16/4 = 4m/s.
Time taken by John to run 84m = time taken by Sam to run 100m = 84/4 = 21 seconds.

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