Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

25 Oct 2012, 20:44

6

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

66% (01:02) correct
34% (01:05) wrong based on 397 sessions

HideShow timer Statistics

Mark biked from his house to his friend's house in how many hours?

(1) Mark bikes at an average speed of 72 blocks per hour.

(2) If Mark could bike an extra 8 blocks for each hour, he would have arrived at his friend's place 1 hour earlier

I got the correct answer (no spoilers!) but if I were to sit down and calculate the answer, how would I do it (I know purpose is not to calculate in DS, but it's really for practice, if anything).

Mark biked from his house to his friend's house in how many hours?

1. Mark bikes at an average speed of 72 blocks per hour.

2. If Mark could bike an extra 8 blocks for each hour, he would have arrived at his friend's place 1 hour earlier

I got the correct answer (no spoilers!) but if I were to sit down and calculate the answer, how would I do it (I know purpose is not to calculate in DS, but it's really for practice, if anything).

Thanks again.

Mark bikes at an average speed of 72 blocks per hour. Mark could bike an extra 8 blocks for each hour = 80 blocks per hour

LCM of 72 & 80 = 720. Time taken by Mark = 720/72 = 10 hrs.

Cheers!
_________________

----------------------------------------------------------------------------------------- What you do TODAY is important because you're exchanging a day of your life for it! -----------------------------------------------------------------------------------------

In all cases, if the speed increases by 1/x, the time taken decreases by 1/x+1 (as speed and time taken are inversely proportional to each other).

In this case the increase in speed is 1/9 (Mark's new speed is 72+8=80 blocks per hour, and the increase of 8 blocks per hour is 1/9th of his previous speed).

Therefore the corresponding decrease in time = 1/9+1 = 1/10. This represents 1/10th of the actual time taken.

1/10th of the actual time taken is given as 1 hour. Hence the total time taken is 10 hours.

Re: Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

01 Aug 2013, 13:08

1

This post received KUDOS

Mark biked from his house to his friend's house in how many hours?

Time = Distance/Speed

(1) Mark bikes at an average speed of 72 blocks per hour. There is no information given about the distance Mark has to travel. All we know is that r=72 INSUFFICIENT

(2) If Mark could bike an extra 8 blocks for each hour, he would have arrived at his friend's place 1 hour earlier t-1 = d/(r+8) We can try and plug in various other distance/time/rate formulas to try and cancel out variables but it's unlikely that will leave us with only one given that there are three variables to plug in for. INSUFFICIENT

1+2) r=72 and t-1 = d/(r+8) We can plug in for r but we still have variables t and d left. d=r*t. If we were to substitute for d we could cancel out t leaving us with just t, as we are looking for the time it took him to bike to his friends house. t-1 = d/(r+8) t-1 = r*t/(72+8) t-1 = 72*t/(80) 80(t-1) = 72t 80t-80=72t 8t=80 t=10 SUFFICIENT

Re: Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

24 Oct 2013, 21:41

WholeLottaLove wrote:

Mark biked from his house to his friend's house in how many hours?

Time = Distance/Speed

(1) Mark bikes at an average speed of 72 blocks per hour. There is no information given about the distance Mark has to travel. All we know is that r=72 INSUFFICIENT

(2) If Mark could bike an extra 8 blocks for each hour, he would have arrived at his friend's place 1 hour earlier t-1 = d/(r+8) We can try and plug in various other distance/time/rate formulas to try and cancel out variables but it's unlikely that will leave us with only one given that there are three variables to plug in for. INSUFFICIENT

1+2) r=72 and t-1 = d/(r+8) We can plug in for r but we still have variables t and d left. d=r*t. If we were to substitute for d we could cancel out t leaving us with just t, as we are looking for the time it took him to bike to his friends house. t-1 = d/(r+8) t-1 = r*t/(72+8) t-1 = 72*t/(80) 80(t-1) = 72t 80t-80=72t 8t=80 t=10 SUFFICIENT

(C)

if we take only second statement (x+8)(t-1)=distance to his friends home=xt.................cant we find t from here ? what am i doing wrong

Mark biked from his house to his friend's house in how many hours?

Time = Distance/Speed

(1) Mark bikes at an average speed of 72 blocks per hour. There is no information given about the distance Mark has to travel. All we know is that r=72 INSUFFICIENT

(2) If Mark could bike an extra 8 blocks for each hour, he would have arrived at his friend's place 1 hour earlier t-1 = d/(r+8) We can try and plug in various other distance/time/rate formulas to try and cancel out variables but it's unlikely that will leave us with only one given that there are three variables to plug in for. INSUFFICIENT

1+2) r=72 and t-1 = d/(r+8) We can plug in for r but we still have variables t and d left. d=r*t. If we were to substitute for d we could cancel out t leaving us with just t, as we are looking for the time it took him to bike to his friends house. t-1 = d/(r+8) t-1 = r*t/(72+8) t-1 = 72*t/(80) 80(t-1) = 72t 80t-80=72t 8t=80 t=10 SUFFICIENT

(C)

if we take only second statement (x+8)(t-1)=distance to his friends home=xt.................cant we find t from here ? what am i doing wrong

Please try to solve and you'll get the answer yourself.
_________________

Re: Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

15 Jan 2015, 13:50

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Re: Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

26 Sep 2016, 18:37

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Mark biked from his house to his friend's house in how many [#permalink]

Show Tags

16 Oct 2016, 09:10

Let's assume that distance between the two houses is x blocks.

(1) With only avg. speed given, S = 72 blocks per hour, and no other information, it not possible to find the time. One equation, two variables \(t = \frac{x}{72}\) INSUFFICIENT

(2) Given \(\frac{x}{S} = \frac{x}{(S+8)} + 1\), equation with two variables and no other constraints on x or/and S, it can not be solved. INSUFFICIENT

However, combining (1) and (2), we can see that substituting value of S in (2) will give us x and then we can get time using \frac{x}{S}. (We don't even need to calculate the exact values.) Hence, (1) and (2) together are SUFFICIENT.