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Help with 2 maths questions from GMATPrep please !

This topic has 3 member replies
GMAT? Senior | Next Rank: 100 Posts Default Avatar
Joined
29 Sep 2006
Posted:
46 messages

Help with 2 maths questions from GMATPrep please !

Post Sat Dec 09, 2006 6:48 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Please can someone explain how to approah and solve the following two problems:

    1. (1/4)^m x (1/5)^18 = 1/2(10)^35. What is m?

    2. 2^x - 2^x-2 = 3(2^13)

    All help would be really appreciated.

    Thanks

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    Post Sat Dec 09, 2006 8:22 am
    Hi GMAT?,

    There is a slight typo in your first problem statement. I have rephrased the question correctly.

    Problem#1 (1/4)^18 x (1/5)^m = 1/2(10)^35. What is m?

    (1/2^2)^18 x (1/5^m) = 1/2(2 x 5)^35 = 1/(2^1 x 2^35 x 5^35)

    (1/2^36) x (1/5^m) = 1/(2^36 x 5^35)

    Equating the exponents of 5, we obtain m = 35.


    Problem#2. 2^x - 2^x-2 = 3(2^13)

    2^x - 2^x-2 = 3(2^13)

    2^x - (2^x)/2^2 = 3(2^13)

    Factor 2^x,

    2^x (1 - 1/4) = 3(2^13)

    2^x * (3/4) = 3(2^13)

    Multiple both sides by 4/3 to obtain:

    2^x = 4 * 2^13 = 2^2 * 2^13 = 2^15

    Equating the exponents, we obtain x = 15

    Cheers,
    Mark

    GMAT? wrote:
    Please can someone explain how to approah and solve the following two problems:

    1. (1/4)^m x (1/5)^18 = 1/2(10)^35. What is m?

    2. 2^x - 2^x-2 = 3(2^13)

    All help would be really appreciated.

    Thanks

    GMAT? Senior | Next Rank: 100 Posts Default Avatar
    Joined
    29 Sep 2006
    Posted:
    46 messages
    Post Sat Dec 09, 2006 8:51 am
    Thanks for your help Mark, it is much appreciated.

    I'm having alot of difficulty understanding these complex exponent and square root problems.

    I don't have a maths background - I'm a medical doctor. I know the rules of exponents but find them difficult to apply in this type of situation.

    Do you know of any good resources where I could get lots of pratice for this type of problem.

    My exam is in 5 days - Maybe it would be best to just concentrate and try to improve what I already know rather then start learning diffcult maths.

    What do you think?

    aim-wsc Legendary Member
    Joined
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    801-
    Post Sat Dec 09, 2006 8:37 pm
    it's OK with me since, i had seen those problems and knew the answers (& how to solve them)

    but i am afraid for other readers who never seen the problems before might find some difficulty in understanding the problems let alone know the explanation.
    its not me not you but the stupid computer's inablity to print/output the math equations/expressions.

    so we might want to try something like this (with neat handwriting Wink )
    Laughing

    or may be we can try drawing in word document-use print screen tool - publish it on post as a picture file.

    great efforts Mark.
    thank you.

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