1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

SAT question

  1. Apr 19, 2008 #1
    1. The problem statement, all variables and given/known data

    let x and y be positive integers and n = x^y
    If n + n^(1/2) + n ^(1/3) = 76, then x cannot equal
    A. 64
    B. 16
    C. 8
    D. 4
    E. 2

    2. Relevant equations

    3. The attempt at a solution

    i really don't know how to approach this question. i tried simplifying the powers and write them in terms of x and y, e.g. x^y + x^(y/2) + x ^(y/3) = 76 and i expressed the answers as powers of 2 but i couldn't find a way out.
  2. jcsd
  3. Apr 19, 2008 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Start by letting x=64. Then by inspection it is clear that for y=1, you get 76. Then try to express 64 as integer powers of the other answer choices. If you do that then you will find the one answer choice that doesn't work by exhausting the answer choices that do work.
  4. Apr 20, 2008 #3
    2, 4 and 8 can be expressed as integer powers of 64. but actually the answer is 8 but not 16... :S
  5. Apr 20, 2008 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    And how exactly did you decide that? Since 82= 64, taking x= 8, y= 2 obviously does satisfy the equation and x= 8 is not the answer.
  6. Apr 20, 2008 #5
    awww..... i'm terribly sorry!!!

    i misread the answer off the book.....

    thanks a loot for helping
  7. Apr 21, 2008 #6


    User Avatar
    Staff Emeritus
    Science Advisor

    Do we get to share in the loot?
  8. Apr 21, 2008 #7
    ok, loot = lot!! ;)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: SAT question
  1. SAT Graphing Question (Replies: 2)

  2. SAT MATH QUESTIOn (Replies: 2)