This post is about subtraction, which is typically difficult for students to learn and for teachers to teach. Think about 503 – 398, for example. To estimate the answer, I can change the problem to 500 – 400 (rounding 503 to 500 and 398 to 400). That gives me an estimate of 100, which I know is close. But how can I know if the actual answer to 503 – 398 is greater or less than 100? I raised this question with third graders.
Several months ago I received an email message from my friend Sandra. She wrote, "If you want something new to distract you, try playing the new game 2048. I’m finding it addicting." I took Sandra’s advice and downloaded the free app. And, like Sandra, I found it addicting. But it also led me to think more about what I think is important when we teach math.
My 15-year-old granddaughter Charlotte is a diligent math student. When I checked recently to see how she was doing with her Algebra 2 math homework, I found her sitting on her bed with her computer, iPad, and phone, managing to text friends on and off as she worked. She asked me for help.