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weight problem

This topic has 6 expert replies and 5 member replies
sportypk Junior | Next Rank: 30 Posts Default Avatar
Joined
31 Mar 2008
Posted:
15 messages

weight problem

Post Fri May 30, 2008 8:57 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    If Jake loses 8 pounds, he will weigh twice as much as his
    sister. Together they now weigh 278 pounds. What is Jake's
    present weight, in pounds?
    (A) 131
    (B) 135
    (C) 139
    (D) 147
    (E) 188

    the OA is 188. how?

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    Post Fri May 30, 2008 9:00 am
    x = weight of Jake's sister

    2x + 8 = Jake's weight

    278 = Jake's sister's weight + Jake's weight

    278 = x + (2x + 8)

    278 = 3x + 8

    270 = 3x

    x = 90

    Thus, Jake's weight = 2x + 8 = 2*90 + 8 = 188

    Thanked by: sportypk
    egybs Master | Next Rank: 500 Posts Default Avatar
    Joined
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    Test Date:
    08/2008
    GMAT Score:
    99%+
    Post Fri May 30, 2008 9:08 am
    Even easier -

    we know that

    J-8 = 2S
    Therefore S = (J-8 )/2

    So J + .5J -4 = 278

    (3/2)J = 282
    J = 188

    Thanked by: sportypk
    sportypk Junior | Next Rank: 30 Posts Default Avatar
    Joined
    31 Mar 2008
    Posted:
    15 messages
    Post Fri May 30, 2008 9:19 am
    wow i feel like the queen of silly mistakes...thanks guys...

    Post Wed Jun 24, 2015 3:21 am
    sportypk wrote:
    If Jake loses 8 pounds, he will weigh twice as much as his
    sister. Together they now weigh 278 pounds. What is Jake�s
    present weight, in pounds?
    (A) 131
    (B) 135
    (C) 139
    (D) 147
    (E) 188

    the OA is 188. how?
    Solution:

    This problem can be solved as a simple word problem in which we must convert words to math. Before we create our equations, we want to define some variables.

    J = Jake’s current weight, in pounds

    S = Sister’s current weight, in pounds

    We are told that “If Jake loses 8 pounds, he will weigh twice as much as his sister." We put this into an equation:

    J - 8 = 2S

    We can isolate J by adding 8 to 2S:

    J = 2S + 8 (Equation 1)

    Next, we are told that “Together they now weigh 278 pounds.” We can also put this into an equation.

    J + S = 278 (Equation 2)

    To solve this equation, we can substitute 2S + 8 from Equation 1 for the variable J in Equation 2:

    2S + 8 + S = 278

    3S = 270

    S = 90

    We now know that the sister weighs S = 90 pounds, and we can plug that value into either equation to determine J. Let’s plug 90 for S into equation 2:

    J + 90 = 278

    J = 188

    Answer: E

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    Post Wed Jun 24, 2015 6:15 am
    sportypk wrote:
    If Jake loses 8 pounds, he will weigh twice as much as his
    sister. Together they now weigh 278 pounds. What is Jake�s
    present weight, in pounds?
    (A) 131
    (B) 135
    (C) 139
    (D) 147
    (E) 188
    Here's a solution that uses one variable.

    Let x = Jake's present weight in pounds
    So, x - 8 = Jake's hypothetical weight IF he were to lose 8 pounds

    If Jake loses 8 pounds, he will weigh twice as much as his sister.
    In other words, the sister weighs HALF as much as Jake's hypothetical weight of x - 8 pounds
    So, (x - 8)/2 = sister's present weight

    Together they NOW weigh 278 pounds.
    So, Jake's present weight + sister's present weight = 278
    So, x + (x - 8)/2 = 278
    Eliminate fractions by multiplying both sides by 2 to get: 2x + (x - 8) = 556
    Simplify: 3x - 8 = 556
    Add 8 to both sides: 3x = 564
    Solve: x = 188 = E

    Cheers,
    Brent

    _________________
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    Post Wed Jun 24, 2015 6:40 am
    sportypk wrote:
    If Jake loses 8 pounds, he will weigh twice as much as his
    sister. Together they now weigh 278 pounds. What is Jake�s
    present weight, in pounds?
    (A) 131
    (B) 135
    (C) 139
    (D) 147
    (E) 188
    ALWAYS KEEP YOUR EYE ON THE ANSWER CHOICES.

    If Jake loses 8 pounds, he will weigh twice as much as his sister.
    j-8 = 2s
    j = 2s + 8 = even + even = even.

    Since Jake's weight must be an EVEN VALUE, the correct answer is E.

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    For more information, please email me at GMATGuruNY@gmail.com.

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    egybs Master | Next Rank: 500 Posts Default Avatar
    Joined
    14 May 2008
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    178 messages
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    99%+
    Post Wed Jun 24, 2015 7:10 am
    GMAT 'experts', I still like my solution from 7 years ago better.

    Post Wed Jun 24, 2015 7:17 am
    GMATGuruNY wrote:
    sportypk wrote:
    If Jake loses 8 pounds, he will weigh twice as much as his
    sister. Together they now weigh 278 pounds. What is Jake�s
    present weight, in pounds?
    (A) 131
    (B) 135
    (C) 139
    (D) 147
    (E) 188
    ALWAYS KEEP YOUR EYE ON THE ANSWER CHOICES.

    If Jake loses 8 pounds, he will weigh twice as much as his sister.
    j-8 = 2s
    j = 2s + 8 = even + even = even.

    Since Jake's weight must be an EVEN VALUE, the correct answer is E.
    Sweeeeeeeeeet! Smile

    Cheers,
    Brent

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

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    Post Wed Jun 24, 2015 9:37 am
    Hi All,

    The answer choices in this question are 'spread out' in such a way that we can get to the correct answer with just a bit of logical thinking.

    We're told that the total weight of Jake and his sister = 278 pounds. We're also told that if Jake LOST 8 pounds, he would TWICE as much as his sister....

    This means that Jake weighs MORE than twice his sister RIGHT NOW. Since the total is 278 pounds, Jake's weight MUST make up MOST of that total weight (a lot more than half). There's only one answer that fits....

    Final Answer: E

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

    _________________
    Contact Rich at Rich.C@empowergmat.com

    Post Wed Jun 24, 2015 1:28 pm
    Rich.C@EMPOWERgmat.com wrote:
    Hi All,

    The answer choices in this question are 'spread out' in such a way that we can get to the correct answer with just a bit of logical thinking.

    We're told that the total weight of Jake and his sister = 278 pounds. We're also told that if Jake LOST 8 pounds, he would TWICE as much as his sister....

    This means that Jake weighs MORE than twice his sister RIGHT NOW. Since the total is 278 pounds, Jake's weight MUST make up MOST of that total weight (a lot more than half). There's only one answer that fits....

    Final Answer: E

    GMAT assassins aren't born, they're made,
    Rich
    Another sweeeeet answer!
    And here I'm using algebra like some sucker!! Smile

    I love seeing how many approaches one can take with a GMAT math question!!!

    I've already reached my exclamation mark quota for the day, so I hope no one else presents more awesome approaches.

    Cheers,
    Brent

    _________________
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    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

    Ian Stewart GMAT Instructor
    Joined
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    Posted:
    2285 messages
    Followed by:
    344 members
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    1090 times
    GMAT Score:
    780
    Post Wed Jun 24, 2015 3:15 pm
    Mitch's solution is obviously fastest, but there is a no-variable solution we can use if the answer choices don't allow for any trick: if Jake loses 8 pounds, then together they'll weigh 270 pounds, and if Jake would then weigh twice as much as his sister, the ratio of their weights is 2 to 1, so Jake would weigh 2/3 of 270, or 180 pounds. Add back the 8, and 188 is the answer.

    _________________
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