Continuing the process of letting some ideas breath on the blog this summer. Here’s another.

It’s a simple activity for those few unexpected extra minutes near the end of the period…or if I just want to hit them with some quick mental stimulation. I picked it up from my fourth grade teacher: mental math.

I simply call out a sequence of operations with a pause between each operation. For example, I might say “2 plus 5 (pause)…times 8 (pause)…minus 10 (pause)…divided 13…what’s the answer?”

Students can’t allowed to say anything out loud and, obviously, any electronic device is prohibited. I don’t require that everyone plays (most do). The students must wait until I say ‘What’s the answer?’ before raising their hands. I call on a different student each time and if that person’s answer is wrong, someone else gets a chance. Because it’s a terribly simple idea, it’s always engaging. The trick is to make it challenging to the point where they get hooked and want more.

Some tidbits: I’ll usually start with one that’s pretty straightforward with long pauses – especially at the beginning of the year. Things get interesting when I start to call out the operations lightning fast or the sequence contains something like 15 operations. Make things fun by using numbers in the millions – or even billions. Also, depending on the class, the level of the math can vary from basic arithmetic to roots and exponents to evaluating trig functions. It’s endless. And fun.