Monthly Calendar Math Trick - 3 x 3 Grid Additions -Step by Step Instructions - Tutorial

There is a simple way to find the sum of all 9 numbers in a 3 x 3 grid on any monthly calendar. Watch the video for all the details. Simply multiply the middle number by 9, to get the sum of all nine numbers in the 3 x 3 grid. This video also shows why this trick works for any 3 x 3 grid on a calendar for any month and any year.