• Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT

OG 13 - PS 145

This topic has 4 expert replies and 2 member replies
gdshamain Senior | Next Rank: 100 Posts Default Avatar
Joined
09 Jan 2014
Posted:
41 messages

OG 13 - PS 145

Post Sat May 03, 2014 1:34 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    145. In a small snack shop, the average(arithmetic mean)
    revenue was $400 per day overall 10-day period.
    During this period,if the average daily revenue was
    $360 for the first 6 days,what was the average daily
    revenue for the last 4 days?
    (A) $420
    (B) $440
    (C) $450
    (D) $460
    (E) $480

    Just wanted to know an alternate method for this one.
    Can we solve this problem using weighted average logic ? ( with the horizontal axes logic)

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    Post Sat May 03, 2014 2:02 pm
    Hi gdshamain,

    There are a number of ways to "do the math" on this type of question. Using the standard Average Formula will work perfectly here, and you'll be asked to use it a couple of times over the course of the Quant section, so you shouldn't try to avoid it.

    That having been said, there's a weighted average "pattern" that can be used against this question:

    The average of the 10 days = $400

    The average for the first 6 days = $360. This means that, on each of the first 6 days, each day was $40 "behind" the average. To get the average "up" to $400, the remaining 4 days have to "make up" for that deficit…

    6 x $40 = $240 "behind"

    The last 4 days have to be above 400 by an amount that will make up for the $240.

    $240/4 = $60. This means that each of the last 4 days needs to be $460 for the overall average to be $400.

    Final Answer: D

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

    _________________
    Contact Rich at Rich.C@empowergmat.com

    gdshamain Senior | Next Rank: 100 Posts Default Avatar
    Joined
    09 Jan 2014
    Posted:
    41 messages
    Post Sat May 03, 2014 2:29 pm
    Thanks for the explanation Rich.

    Post Sat May 03, 2014 4:51 pm
    gdshamain wrote:
    145. In a small snack shop, the average(arithmetic mean)
    revenue was $400 per day overall 10-day period.
    During this period, if the average daily revenue was
    $360 for the first 6 days, what was the average daily
    revenue for the last 4 days?
    (A) $420
    (B) $440
    (C) $450
    (D) $460
    (E) $480

    Here's another approach:

    If the average (mean) daily revenue over 10 days is $400/day, then the TOTAL 10-DAY REVENUE = (10)($400) = $4000

    The average daily revenue for the first 6 days is $360. So, the TOTAL 6-DAY REVENUE = (6)($360) = $2160

    So, the TOTAL REVENUE for the last 4 days = $4000 - $2160 = $1840
    So, the AVERAGE daily revenue for those 4 days = $1840/4 = $460

    Answer: D

    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
    Come see all of our free resources

    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!

    GMAT/MBA Expert

    Post Mon Jun 29, 2015 7:20 am
    gdshamain wrote:
    145. In a small snack shop, the average(arithmetic mean)
    revenue was $400 per day overall 10-day period.
    During this period,if the average daily revenue was
    $360 for the first 6 days,what was the average daily
    revenue for the last 4 days?
    (A) $420
    (B) $440
    (C) $450
    (D) $460
    (E) $480

    Just wanted to know an alternate method for this one.
    Can we solve this problem using weighted average logic ? ( with the horizontal axes logic)
    Solution:

    This problem tests us on our knowledge of weighted averages. To solve, we set up a weighted average equation:

    (Revenue for first 6 days + Revenue for final 4 days)/10 days = 400

    We know that the average revenue for the first 6 days was $360, resulting in total revenue for the first 6 days as 2,160. We let r be the average daily revenue for the final four days, so we have

    (360 x 6 + 4r)/10 = 400

    2,160 + 4r = 4,000

    4r = 1,840

    r = 460

    Answer:D

    _________________

    Scott Woodbury Stewart Founder & CEO
    GMAT Quant Self-Study Course - 500+ lessons 3000+ practice problems 800+ HD solutions
    5-Day Free Trial 5-DAY FREE, FULL-ACCESS TRIAL TTP QUANT

    Post Mon Jun 29, 2015 7:54 am
    Quote:
    145. In a small snack shop, the average(arithmetic mean)
    revenue was $400 per day overall 10-day period.
    During this period,if the average daily revenue was
    $360 for the first 6 days,what was the average daily
    revenue for the last 4 days?
    (A) $420
    (B) $440
    (C) $450
    (D) $460
    (E) $480

    Just wanted to know an alternate method for this one.
    Can we solve this problem using weighted average logic ? ( with the horizontal axes logic)
    We could also do a little fancy number line action. If the average revenue was $360 for the first 6 days, and we're looking for the average revenue for last 4 days, we can depict the distance of each value from the overall average ($400) as 4x and 6x. See here:


    ttp://postimg.org/image/dwcy0k8i9/" target="_blank">

    If 4x = 40, then x = 10 and 6x = 6*10 = 60.
    400 + 60 = 460.

    _________________
    Veritas Prep | GMAT Instructor

    Veritas Prep Reviews
    Save $100 off any live Veritas Prep GMAT Course

    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!

    GMAT/MBA Expert

    Post Mon Jun 29, 2015 3:19 pm
    Another approach:

    To have an average of $400 over 10 days, we need total revenue of $400*10 = $4000.

    So far we have $360*6 = $2160, so we need $4000 - $2160 = $1840 over four days. $1840 / 4 = $460, and we're done!

    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!

    Best Conversation Starters

    1 lheiannie07 116 topics
    2 ardz24 64 topics
    3 swerve 63 topics
    4 LUANDATO 62 topics
    5 M7MBA 57 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    170 posts
    2 image description EconomistGMATTutor

    The Economist GMAT Tutor

    129 posts
    3 image description Rich.C@EMPOWERgma...

    EMPOWERgmat

    122 posts
    4 image description GMATGuruNY

    The Princeton Review Teacher

    121 posts
    5 image description Scott@TargetTestPrep

    Target Test Prep

    118 posts
    See More Top Beat The GMAT Experts