Secret:
This trick relies on the fact that every column under the number one always adds up to 75. This works for every month except February. (It does however work for a February during a leap year.) Check out a monthly calendar and you’ll see that the numbers in the column under the one are 1, 8, 15, 22 and 29. These numbers total 75.
Preparation
Have a yearly calendar nearby that you can quickly reference. Write the number 75 on a piece of paper and fold it up.
