• Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas 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

DS problems

This topic has 6 member replies
gabriel Legendary Member
Joined
20 Dec 2006
Posted:
986 messages
Followed by:
1 members
Thanked:
51 times

DS problems

Post Wed Apr 18, 2007 11:05 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    guys here are some good DS problems ... try and solve them ..

    q.) Train A leaves New York for Boston at 3 PM and travels at the constant speed of 100 mph. An hour later, it passes Train B, which is making the trip from Boston to New York at a constant speed. If Train B left Boston at 3:50 PM and if the combined travel time of the two trains is 2 hours, what time did Train B arrive in New York?
    (1) Train B arrived in New York before Train A arrived in Boston.

    (2) The distance between New York and Boston is greater than 140 miles.

    (A) Statement (1) alone is sufficient, but statement (2) alone is not sufficient.
    (B) Statement (2) alone is sufficient, but statement (1) alone is not sufficient.
    (C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
    (D) Each statement ALONE is sufficient.
    (E) Statements (1) and (2) TOGETHER are NOT sufficient.


    q.)Last Friday a certain shop sold 3/4 of the sweaters in its inventory. Each sweater sold or $20. What was the total revenue last Friday from the sale of these sweaters?

    (1) When the shop opened last Friday, there were 160 sweaters in its inventory.
    (2) All but 40 sweaters in the shop's inventory were sold last Friday.

    A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
    B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
    C BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
    D EACH Statement ALONE is sufficient.
    E Statements (1) and (2) TOGETHER are NOT sufficient.

    q.) 8x(y^3) + 8 (x^3)y = [2(x^2)(y^2)] / [2^(-3)]

    What is xy?

    (1) y>x
    (2) x<0

    (A) Statement (1) alone is sufficient, but statement (2) alone is not sufficient.
    (B) Statement (2) alone is sufficient, but statement (1) alone is not sufficient.
    (C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
    (D) Each statement ALONE is sufficient.
    (E) Statements (1) and (2) TOGETHER are NOT sufficient.

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    jayhawk2001 Community Manager
    Joined
    28 Jan 2007
    Posted:
    789 messages
    Followed by:
    1 members
    Thanked:
    29 times
    Post Wed Apr 18, 2007 9:34 pm
    Gabriel, I had a good mental workout Smile. I seriously hope such
    questions won't show up on GMAT or show up as experimental
    questions.

    gabriel wrote:
    guys here are some good DS problems ... try and solve them ..

    q.) Train A leaves New York for Boston at 3 PM and travels at the constant speed of 100 mph. An hour later, it passes Train B, which is making the trip from Boston to New York at a constant speed. If Train B left Boston at 3:50 PM and if the combined travel time of the two trains is 2 hours, what time did Train B arrive in New York?
    (1) Train B arrived in New York before Train A arrived in Boston.

    (2) The distance between New York and Boston is greater than 140 miles.

    I think it should be D.

    The question stem can be translated into equations of the form below --

    x = distance between NY and BOS
    B = speed of train B

    We know x/100 + x/B = 2
    and 100 + B/6 = x (for train B to reach NY, it has to travel x distance)

    Using 2 in 1, we get

    B^2 - 500B + 60000 = 0
    B = 200 or 300
    Correspondingly x = 150 or 800/6

    1 tells us that B arrived before A. Only B=300 satisfies this.
    If we choose B=200, A will arrive at 4:20 and B will arrive at 4:30
    If we choose B=300, A will arrive at 4:30 and B will arrive at 4:20


    2 tells us that x > 140 which implies it has to be 150 and hence
    sufficient.


    gabriel wrote:
    q.)Last Friday a certain shop sold 3/4 of the sweaters in its inventory. Each sweater sold or $20. What was the total revenue last Friday from the sale of these sweaters?

    (1) When the shop opened last Friday, there were 160 sweaters in its inventory.
    (2) All but 40 sweaters in the shop's inventory were sold last Friday.
    1 - sufficient. 3/4 * 160 * 20 is the revenue
    2 - sufficient. 1/4 of inv = 40, so 3/4 = 120. So revenue = 120 * 20

    Hence D


    gabriel wrote:
    q.) 8x(y^3) + 8 (x^3)y = [2(x^2)(y^2)] / [2^(-3)]

    What is xy?

    (1) y>x
    (2) x<0

    We can translate the equation to

    8xy (x^2 + y^2) = 8xy(2xy)
    8xy*(x-y)^2 = 0

    So, xy = 0 or (x-y)^2 = 0

    1 - sufficient. x-y cannot be zero. So xy = 0

    2 - insufficient. If x = y, then xy need not be zero. If x != y, then xy = 0

    So, I think it should be A

    Prasanna Master | Next Rank: 500 Posts
    Joined
    26 Feb 2007
    Posted:
    418 messages
    Thanked:
    24 times
    Post Fri Apr 20, 2007 6:05 am
    Hi

    I am unable to understand the second equation you had derived in the first problem.

    "and 100 + B/6 = x (for train B to reach NY, it has to travel x distance)"

    Request you to help.

    Prasanna

    jayhawk2001 Community Manager
    Joined
    28 Jan 2007
    Posted:
    789 messages
    Followed by:
    1 members
    Thanked:
    29 times
    Post Fri Apr 20, 2007 5:45 pm
    Prasanna wrote:
    Hi

    I am unable to understand the second equation you had derived in the first problem.

    "and 100 + B/6 = x (for train B to reach NY, it has to travel x distance)"

    Request you to help.

    Prasanna
    x is the total distance between NY and BOS. We know the 2 trains meet
    at a point which is 100 miles from NY.

    We also know that B * 10min/60min is the total distance that B would have
    traveled from BOS to the point in between.

    So, 100 + B/6 = x

    gabriel Legendary Member
    Joined
    20 Dec 2006
    Posted:
    986 messages
    Followed by:
    1 members
    Thanked:
    51 times
    Post Sat Apr 21, 2007 1:14 am
    jayhawk2001 wrote:
    Gabriel, I had a good mental workout Smile. I seriously hope such
    questions won't show up on GMAT or show up as experimental
    questions.

    gabriel wrote:
    guys here are some good DS problems ... try and solve them ..

    q.) Train A leaves New York for Boston at 3 PM and travels at the constant speed of 100 mph. An hour later, it passes Train B, which is making the trip from Boston to New York at a constant speed. If Train B left Boston at 3:50 PM and if the combined travel time of the two trains is 2 hours, what time did Train B arrive in New York?
    (1) Train B arrived in New York before Train A arrived in Boston.

    (2) The distance between New York and Boston is greater than 140 miles.

    I think it should be D.

    The question stem can be translated into equations of the form below --

    x = distance between NY and BOS
    B = speed of train B

    We know x/100 + x/B = 2
    and 100 + B/6 = x (for train B to reach NY, it has to travel x distance)

    Using 2 in 1, we get

    B^2 - 500B + 60000 = 0
    B = 200 or 300
    Correspondingly x = 150 or 800/6

    1 tells us that B arrived before A. Only B=300 satisfies this.
    If we choose B=200, A will arrive at 4:20 and B will arrive at 4:30
    If we choose B=300, A will arrive at 4:30 and B will arrive at 4:20


    2 tells us that x > 140 which implies it has to be 150 and hence
    sufficient.


    gabriel wrote:
    q.)Last Friday a certain shop sold 3/4 of the sweaters in its inventory. Each sweater sold or $20. What was the total revenue last Friday from the sale of these sweaters?

    (1) When the shop opened last Friday, there were 160 sweaters in its inventory.
    (2) All but 40 sweaters in the shop's inventory were sold last Friday.
    1 - sufficient. 3/4 * 160 * 20 is the revenue
    2 - sufficient. 1/4 of inv = 40, so 3/4 = 120. So revenue = 120 * 20

    Hence D


    gabriel wrote:
    q.) 8x(y^3) + 8 (x^3)y = [2(x^2)(y^2)] / [2^(-3)]

    What is xy?

    (1) y>x
    (2) x<0

    We can translate the equation to

    8xy (x^2 + y^2) = 8xy(2xy)
    8xy*(x-y)^2 = 0

    So, xy = 0 or (x-y)^2 = 0

    1 - sufficient. x-y cannot be zero. So xy = 0

    2 - insufficient. If x = y, then xy need not be zero. If x != y, then xy = 0

    So, I think it should be A
    excellent dood Very Happy .... u got all of them right ... seems like u ready to take the gmat on (head on) ... these were q's that i got form some other forums ( no copyright issues Very Happy ) ... and they are defnitely in the range of 730 -760 ( i just loved the first q) .. so i dont think u shuld be really worried abt the quant part anymore ..

    f2001290 Master | Next Rank: 500 Posts
    Joined
    10 Mar 2007
    Posted:
    400 messages
    Followed by:
    1 members
    Thanked:
    1 times
    Post Sat Apr 21, 2007 2:48 am
    1st and 3rd questions have broken my confidence.

    Gabriel - what is the beat strategy to solve these sort of questions?

    Prasanna Master | Next Rank: 500 Posts
    Joined
    26 Feb 2007
    Posted:
    418 messages
    Thanked:
    24 times
    Post Sat Apr 21, 2007 4:19 pm
    Thanks...How stupid I was

    Best Conversation Starters

    1 Vincen 180 topics
    2 lheiannie07 65 topics
    3 Roland2rule 49 topics
    4 ardz24 44 topics
    5 LUANDATO 23 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

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

    EMPOWERgmat

    103 posts
    3 image description GMATGuruNY

    The Princeton Review Teacher

    102 posts
    4 image description EconomistGMATTutor

    The Economist GMAT Tutor

    94 posts
    5 image description DavidG@VeritasPrep

    Veritas Prep

    76 posts
    See More Top Beat The GMAT Experts