January 22, 2019 January 22, 2019 10:00 PM PST 11:00 PM PST In case you didn’t notice, we recently held the 1st ever GMAT game show and it was awesome! See who won a full GMAT course, and register to the next one. January 26, 2019 January 26, 2019 07:00 AM PST 09:00 AM PST Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
Author 
Message 
TAGS:

Hide Tags

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8806
Location: Pune, India

"A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
25 Jul 2016, 04:08
Question Stats:
65% (02:22) correct 35% (02:39) wrong based on 101 sessions
HideShow timer Statistics
Responding to a pm: "A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap? A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point). A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds. In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs Answer (A)
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Board of Directors
Status: Stepping into my 10 years long dream
Joined: 18 Jul 2015
Posts: 3626

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
28 Jul 2016, 09:20
VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) How did you get "In 315 secs, B completes 3.5 laps."? Please elaborate.
_________________
My GMAT Story: From V21 to V40 My MBA Journey: My 10 years long MBA Dream My Secret Hacks: Best way to use GMATClub  Importance of an Error Log! Verbal Resources: All SC Resources at one place  All CR Resources at one place Blog: Subscribe to Question of the Day Blog GMAT Club Inbuilt Error Log Functionality  View More. New Visa Forum  Ask all your Visa Related Questions  here. New! Best Reply Functionality on GMAT Club! Find a bug in the new email templates and get rewarded with 2 weeks of GMATClub Tests for free Check our new About Us Page here.



Current Student
Joined: 18 Oct 2014
Posts: 843
Location: United States
GPA: 3.98

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
28 Jul 2016, 12:56
VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) Hi! VeritasPrepKarishma, Can't there be a possibility that B is in its first lap when A meets B. Also, I am confused that how can A meets B for the first time in the middle of 5th lap since its a circle. Please enlighten.
_________________
I welcome critical analysis of my post!! That will help me reach 700+



Manager
Joined: 20 Mar 2015
Posts: 60
Location: United States
Concentration: General Management, Strategy
WE: Design (Manufacturing)

"A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
28 Jul 2016, 13:32
Draw a circle with 2 ends A' and B'(Diametric) if they both start at A', then mid of 5th lap would mean A is at point B' That means 4.5 laps. Total time : 315 {4.5*70}seconds. B should also be at the same point. Start using options. If we take 90 seconds, a quick glimpse will tell us that 90+90+90+45 (3.5 laps) is also 315 and also the same position i.e. B' Don't need to look further. Hence A is the answer . A quick way of avoiding calculations! Sent from my iPhone using GMAT Club Forum mobile app



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8806
Location: Pune, India

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
28 Jul 2016, 20:48
abhimahna wrote: VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) How did you get "In 315 secs, B completes 3.5 laps."? Please elaborate. DivyadishaA covers 4.5 laps in 315 seconds. This is when they meet. So B has also been running for 315 seconds. How much distance will he cover in this time? Think about it: If B was still on his first lap, A would have met him in his second lap. Why? Because B would be somewhere on the circular path when A takes his second lap. So he would have met B then. But A met him for the first time after 4.5 laps. Since they are both running in the same direction, till the time they cover equal number of laps (perhaps A is very slightly faster than B), they don't meet. B lags behind A. But when A covers a distance of 1 lap more than B, he has to cross B again (since they are running on the same circular path). Try to draw a diagram to imagine it. They meet for the first time when A covers exactly 1 lap more than B.
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Intern
Joined: 21 Jun 2016
Posts: 5

"A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
22 Aug 2016, 04:04
VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) Dear Karishma I have a question on this  when it says A catches B when A is exactly in the middle of the 5 th round does not this mean that 5.5 laps for A and 4.5 laps for B. As I have solved the problem with 5.5 laps in 385 secs (70*5.5) for A and 4.5 Laps for B in the same time frame. And result is 85.5 secs. Can you help where I am doing wrong? Thanks



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8806
Location: Pune, India

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
22 Aug 2016, 04:16
Rasul_Rasul wrote: VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) Dear Karishma I have a question on this  when it says A catches B when A is exactly in the middle of the 5 th round does not this mean that 5.5 laps for A and 4.5 laps for B. As I have solved the problem with 5.5 laps in 385 secs (70*5.5) for A and 4.5 Laps for B in the same time frame. And result is 85.5 secs. Can you help where I am doing wrong? Thanks That's a common mistake. Think about it  when I say, A caught B in the middle of the first round, what does that mean? Does it mean 0.5 or 1.5? The middle of the first round is when A has covered only half a round. So it will be 0.5. Similarly, middle of 5th round is 4 complete rounds and a half. It's the way we think about age. Middle of first year means the baby is only 6 months old. The fifth year is the year that starts after the child completes 4 yrs.
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Intern
Joined: 21 Jun 2016
Posts: 5

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
22 Aug 2016, 21:00
VeritasPrepKarishma wrote: Rasul_Rasul wrote: VeritasPrepKarishma wrote: Responding to a pm:
"A" and "B" run around a circular track starting from the same point simultaneously in the same direction. "A" meets "B" for the first time when "A" is exactly in the middle of his 5th round. If "A" is faster than "B" and take 70 seconds to complete 1 lap, how long will B take to complete 1 lap?
A) 90 seconds B) 54.44 seconds C) 110 seconds D) 63 seconds E) 77 seconds
A is faster than B. Every second he increases distance between A and B. They will meet for the first time again when he increases distance between them by one full circle. (Say the lap is of 100m. He keeps increasing distance between them. When he is 90 m ahead of him, it is the same as 10 m behind him because they are moving in a circle. Finally when he is 100 m ahead of him, he is exactly 1 lap ahead and hence both are at the same point).
A takes 70 secs for one full lap. So he covers 4.5 laps in exactly 70*4.5 = 315 seconds.
In 315 secs, B completes 3.5 laps. So for each lap, he takes 315/3.5 = 90 secs
Answer (A) Dear Karishma I have a question on this  when it says A catches B when A is exactly in the middle of the 5 th round does not this mean that 5.5 laps for A and 4.5 laps for B. As I have solved the problem with 5.5 laps in 385 secs (70*5.5) for A and 4.5 Laps for B in the same time frame. And result is 85.5 secs. Can you help where I am doing wrong? Thanks That's a common mistake. Think about it  when I say, A caught B in the middle of the first round, what does that mean? Does it mean 0.5 or 1.5? The middle of the first round is when A has covered only half a round. So it will be 0.5. Similarly, middle of 5th round is 4 complete rounds and a half. It's the way we think about age. Middle of first year means the baby is only 6 months old. The fifth year is the year that starts after the child completes 4 yrs. Thank you Karishma. I got your point. BR



Manager
Joined: 14 Jun 2018
Posts: 223

Re: "A" and "B" run around a circular track starting from the same point s
[#permalink]
Show Tags
29 Oct 2018, 03:14
Let the time taken by B to complete 1 lap = x seconds. Time taken by A = 70 seconds. Given , A meets B for the first time at the mid point of 5th round = 4.5 * 70 seconds. Therefore , he will me B for the first time at the starting point after 2 * 4.5 * 70 = 630 seconds.
LCM of x and 70 should be 630.
Only A fits




Re: "A" and "B" run around a circular track starting from the same point s &nbs
[#permalink]
29 Oct 2018, 03:14






