Mind Reading Math Trick
Abstract: Learn math by doing a fun number trick!
Grade Level: All ages
Time Needed: 10 minutes
Materials:
 Paper and pencil
 Calculator
Preparations before program:
Procedure:
1. Think of a number, any positive integer (but keep it small so you can do computations in your
head).
a. Square it.
b. Add the result to your original number.
c. Divide by your original number.
d. Add 17.
e. Subtract your original number.
f. Divide by 6.
g. The number you are thinking of now is 3!
References: https://www.math.hmc.edu/funfacts/ffiles/10004.1.shtml
Additional Information:
Additional/Background information:
We can see how this works by using some algebra. If you use X instead of a number, you will see that X
is removed by Step 5.
Choose a number x
Square it: x^2 or (x*x)
Add result to original number: (x*x) + x
Divide by original number: (x*x +x)/x = x + 1
Add 17: x+1 + 17
Subtract the original number: (x + 18) – x = 18
Divide by 6: 18/6
Result: 3