Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: It's all in the list.

  1. Apr 13, 2004 #1
    If x and y are whole numbers that don't have10 as a factor, and if xy = 1,000, find x + y.
     
  2. jcsd
  3. Apr 13, 2004 #2
    You have 2 integers x and y such that their product xy is a multiple of 10, but neither x nor y is a multiple of 10 (the rightmost digit of the product is 0).

    Then the rightmost digit of one of them, let's say y, must be 5, and then x must be an even number. Think about it and you will see that this is the only way to end up with 0 in the 1's column of the product.

    So you can express x and y in a different form:
    x = 2a
    y = 10b + 5
    where a is a non-zero integer and b is an integer (maybe 0).

    Now, find the product in terms of a and b, set that equal to 1000 & see if that helps you find the answer.
     
    Last edited: Apr 14, 2004
  4. Apr 13, 2004 #3
    The steps.

    The answer with the steps to follow.
     
  5. Apr 14, 2004 #4
    I edited my post. See hints above.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook