Detective Work

Purpose:  To show children a math trick while practicing simple math operations

Materials: Pencil, Paper, and Calculator (optional)

Set-Up:  You are a detective trying to figure out your suspect's (partner's) phone number and age.

Activity:

Step 1:  Have your suspect write down their telephone number (do not include the area code), and multiply it by 2.

Step 2:  Have them add 5 and multiply the answer by 50.

Step 3:  Have them add their age and the number of days in one year.

Step 4:  Tell them to subtract 615 from the answer, and have them to write it down and give you the piece of paper with the answer.

After completing the procedure above, see if you notice a pattern in the answer.  Does anything look familar?

The first seven numbers are the suspect's telephone number, and the last digit or digits reflect their age.

(Modified from the book Super Math Tricks, written by Zondra Knapp)

*Graphic from Big Box of Art CD