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

I don't get this

  1. Mar 20, 2004 #1
    It's like a riddle thinger..

    If 9 times 9 is 7
    10 times 9 is 9
    10 times 8 is 8
    8 time 8 is 2

    What is 9 times 7 ?

    It says to "Think mathematically. There is a pattern of calculating involved."

    Anybody got any idea what this is??? What the answer is??
     
  2. jcsd
  3. Mar 20, 2004 #2
    Multiply the numbers (using "normal" multiplication), then take the difference between the digits.

    9 * 9 = 81 and 8 - 1 = 7.
    10 * 9 = 90 and 9 - 0 = 9.
    10 * 8 = 80 and 8 - 0 = 8.
    8 * 8 = 64 and 6 - 4 = 2.

    Since 9 * 7 = 63, the answer you're looking for is probably 6 - 3 = 3.
     
  4. Mar 20, 2004 #3
    Wow.. I never saw that. Thanx
     
  5. Mar 23, 2004 #4

    TeV

    User Avatar

    Utter nonsense.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?