It was parent's night at the school that I teach at this week. There is generally a lot of waiting around for the teachers. So based on the brainteaser over at Text Savvy I decided to give my colleagues a little competition. Just as at Text Savvy the rules were:

1. Write a mathematical expression that evaluates to 9.

2. Use exactly three 3's and no other numerals.

3. Use no plus signs.

The idea was to be the "Most Creative", probably as easy to judge as "learning" so why not. I have to say that I was tremendously impressed with the results. With in the first half hour I had the following entries:

I really thought they were great. Some quibbling could be made with the sin(pi) and the units in the first, but they were creative.

Of course, word spread and the chemistry teacher at the school, who drove home with me on Wednesday came up with the following three in the car, which I think are wonderful too.

All in all a great success.

Tips to promote students' metacognition

18 hours ago

## 2 comments:

Excellent!

The first entry isn't correct until you eliminate the last "in" unit of measure. I explain: the division 3ft/3in = 12, which is a number, not a length. Therefore you may only subtract a number from a number.

Giovanni Ciriani

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