What does the expression above equal?
The Four Fours problem is well known by most Mathematics teachers. Each time I have tried it with year 7 to year 9 classes it has proven to be a great success. You can download my Four_Fours_Grid.xls worksheet by clicking on the Scribd icon at right.
There are many references to this problem on the internet:
1. Wikipedia gives rules and variations as well as solutions for 1 to 20
2. Four Fours Problem compiled by Paul Bourke gives solutions up to 9370240
3. The Definitive Four Fours Answer Key by David A. Wheeler is available as a pdf document
Also of note is the adaption of the problem to other single digit numbers (eg. Four Fives) and to particular years (eg. I first used this in 1984). If you check out the following link you will notice that the answers 1 to 100 are possible for four 3’s, four 4’s, four 5’s, four 9’s, but probably not for the other single digits. Similarly the years 2000 – 2009 are not suitable for this puzzle, but using a student’s year of birth can overcome this.
If you are new to Mathematics teaching, I highly recommend this activity to you. If you are an experienced Maths teacher, why not try one of the variations mentioned above. In any case, post a comment about how the activity went!