1. Limited time only! Sign up for a free 30min personal 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!

B Fun way of doing multiplication with intersecting lines

  1. Mar 19, 2017 #1


    Staff: Mentor

    Here's a fun way to do multiplication graphically that originated in Japan:

  2. jcsd
  3. Mar 20, 2017 #2


    User Avatar
    Gold Member

    Weirdly interesting.
  4. Mar 23, 2017 #3


    User Avatar
    Science Advisor

    It is of course equivalent to the ordinary multiplication algorithm, just doing it graphically instead of numerically.
  5. Mar 23, 2017 #4


    Staff: Mentor

    I wonder if some gifted visual learners could do their math this way mentally.
    Last edited: Mar 23, 2017
  6. Mar 23, 2017 #5


    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    Good method to help. I've done that and used the method to show people how multidigit multiplication works.
  7. Mar 23, 2017 #6


    Staff: Mentor

    It's always interesting to find these alternative multiplication strategies.

    Our times tables and method of multiplying is a result of our place value system with the invention of zero.

    Whereas the Roman numeral system and earlier systems had to use tables of squares and the formula:

    ## 1/4 ((a+b)^2 - (a-b)^2) = a * b##

    ##3*5 = 1/4 * ( 64 - 4 ) = 1/4 * 60 = 15##

    Or the Trachtenberg system of multiplying using rules to follow for each digit of the multiplier over times tables.

    Or the systems created by arithmetic savants with colors and placements that we really don't understand how they do it.

    But my favorite was the slide rule where you got an accurate but not exact answer so that close was good enough.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Fun way of doing multiplication with intersecting lines
  1. Line intersections. (Replies: 2)