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:

Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

11 Dec 2007, 20:57

2

This post received KUDOS

10

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

77% (02:43) correct
23% (02:20) wrong based on 456 sessions

HideShow timer Statistics

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

A. (x + y) / t B. 2(x + t) / xy C. 2xyt / (x + y) D. 2(x + y + t) / xy E. x(y + t) + y(x + t)

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

d = distance in miles

t = (d/2)/x + (d/2)/y
simplify to get: d = 2xyt/(x+y)

How can this be solved by picking nos rather than conventi [#permalink]

Show Tags

11 Sep 2012, 21:26

Hi Guys,

Doubt :How can the below Q be solved by picking nos rather than conventional approach

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

Doubt :How can the below Q be solved by picking nos rather than conventional approach

Thanks,

harikris

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

A. (x + y) / t B. 2(x + t) / xy C. 2xyt / (x + y) D. 2(x + y + t) / xy E. x(y + t) + y(x + t)

Say the distance to school is 10 miles, x=5 miles per hour and y=1 miles per hour, then:

Time Bob spent biking would be 5/5=1 hour, and time he spent walking would be 5/1=5 hours, so t=1+5=6 hours.

Now, plug x=5, y=1, and t=6 into the answer choices to see which one yields the distance of 10 miles. Only answer choice C fits.

Answer: C.

Note that for plug-in method it might happen that for some particular number(s) more than one option may give "correct" answer. In this case just pick some other numbers and check again these "correct" options only.

Re: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

12 Sep 2012, 01:52

7

This post received KUDOS

Whatever wrote:

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

A. (x + y) / t B. 2(x + t) / xy C. 2xyt / (x + y) D. 2(x + y + t) / xy E. x(y + t) + y(x + t)

Distance you can obtain as Rate x Time. Also, you can add/subtract only quantities that have the same units, i.e. you cannot add speed to time. Thus, you can immediately eliminate B, D and E.

A cannot be the correct answer, as it has units of speed over time, not units of distance. You are left with C as the correct answer. _________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

12 Sep 2012, 02:00

1

This post received KUDOS

1

This post was BOOKMARKED

Whatever wrote:

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

A. (x + y) / t B. 2(x + t) / xy C. 2xyt / (x + y) D. 2(x + y + t) / xy E. x(y + t) + y(x + t)

I understood the problem as one of the average speed problems. One quick way to solve is with the direct formula of average speed. Since the speeds for different halves are mentioned, we can use the formula Avg speed = 2ab/(a+b), where a is constant speed for 1st half of journey and b is constant speed for 2nd half of journey. Per the Question Avg speed for total trip = 2xy/(x+y). Therefore the total distance is 2xyt/(x+y).

Hence Answer is C. _________________

Regards SD ----------------------------- Press Kudos if you like my post. Debrief 610-540-580-710(Long Journey): http://gmatclub.com/forum/from-600-540-580-710-finally-achieved-in-4th-attempt-142456.html

Re: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

12 Sep 2012, 04:54

1

This post received KUDOS

1

This post was BOOKMARKED

SOURH7WK wrote:

Whatever wrote:

Bob bikes to school every day at a steady rate of x miles per hour. On a particular day, Bob had a flat tire exactly halfway to school. He immediately started walking to school at a steady pace of y miles per hour. He arrived at school exactly t hours after leaving his home. How many miles is it from the school to Bob's home?

A. (x + y) / t B. 2(x + t) / xy C. 2xyt / (x + y) D. 2(x + y + t) / xy E. x(y + t) + y(x + t)

I understood the problem as one of the average speed problems. One quick way to solve is with the direct formula of average speed. Since the speeds for different halves are mentioned, we can use the formula Avg speed = 2ab/(a+b), where a is constant speed for 1st half of journey and b is constant speed for 2nd half of journey. Per the Question Avg speed for total trip = 2xy/(x+y). Therefore the total distance is 2xyt/(x+y).

Hence Answer is C.

The definition of average speed is \(\frac{Total \, distance}{Total \, time}\). For a particular case when on a fraction \(F\) of the distance \(D\) the speed was \(x\) and on the remaining fraction \((1-F)\) of \(D\) the speed was \(y\) , we can calculate the average speed as:

In our case, \(F=\frac{1}{2}\), and the average speed is indeed \(\frac{2xy}{x+y}\).

I wouldn't say this formula is a must to remember. The definition of average speed, YES and then, depending on the data of the specific question, the average speed can be easily worked out.

Your approach is correct and it follows the path of "let's work out a solution". Although the elimination method is not always possible, I would like to suggest that there is a major takeaway lesson from this question: when variables are used (in our case \(x\) and \(y\) as speeds, \(t\) as time) which have specific units attached, pay attention to the basic rule saying that addition and subtraction has a meaning only when all the terms have the same units. In our case, you cannot add speed to time, so answers involving expressions like \(x+t\) or \(y+t\) can be automatically eliminated. _________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

08 Feb 2014, 23:46

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: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

13 Apr 2014, 06:58

20 seconds if you just read the question and go for the units...I say always checkk the units first for all the options in such type of questions _________________

Appreciate the efforts...KUDOS for all Don't let an extra chromosome get you down..

Re: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

10 Jun 2015, 03:21

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: Bob bikes to school every day at a steady rate of x miles [#permalink]

Show Tags

11 Jun 2016, 11:07

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. _________________

This is the kickoff for my 2016-2017 application season. After a summer of introspect and debate I have decided to relaunch my b-school application journey. Why would anyone want...

Check out this awesome article about Anderson on Poets Quants, http://poetsandquants.com/2015/01/02/uclas-anderson-school-morphs-into-a-friendly-tech-hub/ . Anderson is a great place! Sorry for the lack of updates recently. I...

According to the Nebula Award categories, a novel must be over 40,000 words. In the past year I have written assignments for 22 classes totaling just under 65...