Triathlete Dan

This topic has 3 expert replies and 5 member replies
j_shreyans Legendary Member Default Avatar
Joined
07 Aug 2014
Posted:
510 messages
Followed by:
5 members
Thanked:
3 times

Triathlete Dan

Post Sun Oct 12, 2014 8:06 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 10 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?

    A)1/8
    B)2/15
    C)3/15
    D)1/4
    E)3/8

    OAA

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    Post Sun Oct 12, 2014 11:24 am
    Hi j_shreyans,

    This is a "distance formula" question (that also involves average speed) that gives you all of the information that you need to answer the question, so you just have to plug the numbers into the formulas:

    Distance = Rate x Time

    Running:

    2 miles = (10 miles/hr)(T)
    2/10 = T
    1/5 hour = Time to run

    Swimming:

    2 miles = (6 miles/hr)(T)
    2/6 = T
    1/3 hour = Time to swim

    Total time = 1/5 + 1/3 = 8/15 hours

    For this last series of steps, we have to pay very careful attention the specifics of the question. It asks for average rate in MILES PER MINUTE ( NOT miles per hour), so we'll have to do a little more work to get the answer.

    Average Speed for the entire trip IN MILES PER MINUTE

    Total Distance = (Average Speed) x (Total Time)

    4 miles = (Av. Sp.)(8/15 hours)
    4(15/8) = Av. Sp.
    15/2 miles per HOUR = Av. Sp.

    Since there are 60 minutes per hour, we have to divide this speed by 60...

    (15/2)/60 = miles per MINUTE
    1/8 miles per MINUTE

    Final Answer: A

    GMAT assassins aren't born, they're made,
    Rich

    _________________
    Contact Rich at Rich.C@empowergmat.com

    Thanked by: j_shreyans

    GMAT/MBA Expert

    Post Sun Oct 12, 2014 8:56 pm
    Let's break it up into pieces. We'll change the rates to miles per minute by dividing each rate by 60.

    Swimming:
    D = 2
    R = 1/10

    Time = D/R = 2/(1/10) = 20 minutes

    Running:
    D = 2
    R = 1/6

    Time = D/R = 2/(1/6) = 12 minutes

    He travels 4 miles in 32 minutes. This reduces to 1 mile in 8 minutes, or 1/8 of a mile per minute, so the answer is A.

    Thanked by: j_shreyans
    Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!
    Post Mon Oct 13, 2014 2:45 am
    j_shreyans wrote:
    Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 10 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?

    A)1/8
    B)2/15
    C)3/15
    D)1/4
    E)3/8
    The distance traveled in each direction can be ANY VALUE.
    Let the distance in each direction = 30 miles.

    At a rate of 10mph, the time spent running = d/r = 30/10 = 3 hours.
    At a rate of 6mph, the time spent swimming = d/r = 30/6 = 5 hours.
    Average rate for the entire trip = (total distance)/(total time) = (30+30)/(3+5) = 60/8 = 15/2 miles per hour.

    Since 15/2 miles is traveled each hour, 1/60 of this distance is traveled each minute:
    (1/60)(15/2) = 1/8 miles per minute.

    The correct answer is A.

    _________________
    Mitch Hunt
    GMAT Private Tutor
    GMATGuruNY@gmail.com
    If you find one of my posts helpful, please take a moment to click on the "Thank" icon.
    Available for tutoring in NYC and long-distance.
    For more information, please email me at GMATGuruNY@gmail.com.

    Thanked by: j_shreyans
    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
    Post Tue Oct 14, 2014 8:42 am
    j_shreyans wrote:
    Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 10 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?

    A)1/8
    B)2/15
    C)3/15
    D)1/4
    E)3/8

    OAA
    Average speed = (total distance)/(total time)
    We know the total distance = 4 miles

    The total time consists of two parts:
    Let's begin with a "word equation"
    TOTAL time = (time spent running) + (time spent swimming)

    time = distance/speed
    So, time spent running = 2/10 = 1/5 hours = 12 minutes
    time spent swimming = 2/6 = 1/3 hours = 20 minutes

    TOTAL time = (12 minutes) + (20 minutes)
    = 32 minutes

    AVERAGE speed = (total distance)/(total time)
    = (4 miles)/(32 minutes)
    = 1/8 miles/minute
    = A

    Cheers,
    Brent

    _________________
    Brent Hanneson – Founder of GMATPrepNow.com
    Use our video course along with Beat The GMAT's free 60-Day Study Guide

    Check out the online reviews of our course

    Thanked by: j_shreyans
    GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!
    GMATinsight Legendary Member
    Joined
    10 May 2014
    Posted:
    993 messages
    Followed by:
    21 members
    Thanked:
    203 times
    Post Wed Oct 15, 2014 4:08 am
    j_shreyans wrote:
    Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 10 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?

    A)1/8
    B)2/15
    C)3/15
    D)1/4
    E)3/8

    OAA
    CONCEPT: AVERAGE SPEED = TOTAL DISTANCE / TOTAL TIME

    Total Distance Traveled = 2 (Running) + 2 (Swimming) = 4 miles

    Total Time (Distance/Speed) Taken = (2/10) (Running) + (2/6) (Swimming) = (6+10)/30 = 16/30 = 8/15

    Average Speed = 4 / (8/15) = 15/2 (Miles/Hour)

    Average Speed = (15/2) x (1/60) = 1/8 Miles/Minute

    Answer: Option A

    _________________
    Prosper!!!
    Bhoopendra Singh & Sushma Jha
    "GMATinsight"
    Contact Us
    Testimonials
    To register for One-on-One FREE ONLINE DEMO Class Call/e-mail
    e-mail: info@GMATinsight.com
    Mobile: +91-9999687183 / +91-9891333772
    Get in touch for SKYPE-Based Interactive Private Tutoring
    One-On-One Classes fee - US$30 per hour &
    for FULL COURSE (38 LIVE Sessions)-US$1000

    "Please click on 'Thank' if you like my post/response."

    Classroom Centres Address:
    GMATinsight
    Dwarka, New Delhi-110075 and Shivalik New Delhi

    Joey N Newbie | Next Rank: 10 Posts Default Avatar
    Joined
    31 Jul 2013
    Posted:
    7 messages
    Thanked:
    1 times
    Post Wed Oct 15, 2014 4:49 am
    All of the above approaches are solid - but man, that's not at all how I would do this.

    There is a MUCH easier way - but it takes some out of the box thinking.

    The first thing is to remember that on problem solving you have a HUGE asset - the answer has to be one of the 5 options given to you.

    So....

    The first thing I'd do is convert each answer into miles per hour (easier to think about since the problem is already in mph - why make your life harder by converting into miles/min - SILLY! Don't do it!!!)


    A) (1/8) * 60 = 60/8 = like 7.something (don't need to be accurate - it's actually 7.5 - but we are only looking for some quick rough math)

    B) (2/15)*60 = (quick mental reduction leaves 2*(60/15) -> 2*4 = 8

    C) similar to B -> 12

    D) 60/4 = 15

    E) 3 * answer A = so 21"ish"

    Now, just VISUALIZE the problem right?

    The answer just HAS to be between 10mph and 6mph for it to even be reasonable.

    Therefore, eliminate C, D, E

    Now, 8 mph is the average of 10 and 6, but that's too easy AND you know that on the 10mph leg of the trip - you'll get done faster - so the average speed should be closer to 6 than to 10. (Does that make sense to you?)

    BAM!!!

    A is the only answer left.

    I friggin love the GMAT when it gives softballs like this - but you've got to frame the questions the right way.


    Wanna learn how to take apart the test in this way? Shoot me a pm or email me at joey@strategicgmat.com

    _________________
    Want to 3x your study, time, and results on the GMAT?

    Free report shows you how to get explosive growth on the GMAT.
    Get it here:
    http://bit.ly/GMATleverage

    Thanked by: Harsh@rayal
    Joey N Newbie | Next Rank: 10 Posts Default Avatar
    Joined
    31 Jul 2013
    Posted:
    7 messages
    Thanked:
    1 times
    Post Wed Oct 15, 2014 4:49 am
    Sorry, double post

    _________________
    Want to 3x your study, time, and results on the GMAT?

    Free report shows you how to get explosive growth on the GMAT.
    Get it here:
    http://bit.ly/GMATleverage

    GMATinsight Legendary Member
    Joined
    10 May 2014
    Posted:
    993 messages
    Followed by:
    21 members
    Thanked:
    203 times
    Post Wed Oct 15, 2014 7:49 am
    If getting the quick answer is a concern then I would attempt this question by a straight concept

    Average Speed when the distance is constant in to and fro motion = 2ab / (a+b) = 2x10x6 / (10+6) = 120/16 = 15/2 Miles/hour = 15/(2x60) Miles/Min = 1/8 Miles/Min

    Answer: Option A

    Time taken to solve : 10 Seconds Laughing

    _________________
    Prosper!!!
    Bhoopendra Singh & Sushma Jha
    "GMATinsight"
    Contact Us
    Testimonials
    To register for One-on-One FREE ONLINE DEMO Class Call/e-mail
    e-mail: info@GMATinsight.com
    Mobile: +91-9999687183 / +91-9891333772
    Get in touch for SKYPE-Based Interactive Private Tutoring
    One-On-One Classes fee - US$30 per hour &
    for FULL COURSE (38 LIVE Sessions)-US$1000

    "Please click on 'Thank' if you like my post/response."

    Classroom Centres Address:
    GMATinsight
    Dwarka, New Delhi-110075 and Shivalik New Delhi

    Best Conversation Starters

    1 AbeNeedsAnswers 125 topics
    2 jjjinapinch 82 topics
    3 richachampion 12 topics
    4 saswata4s 10 topics
    5 NandishSS 10 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Matt@VeritasPrep

    Veritas Prep

    120 posts
    2 image description Rich.C@EMPOWERgma...

    EMPOWERgmat

    116 posts
    3 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    93 posts
    4 image description DavidG@VeritasPrep

    Veritas Prep

    75 posts
    5 image description GMATGuruNY

    The Princeton Review Teacher

    62 posts
    See More Top Beat The GMAT Experts