Investigations Blog

I often think about a lesson, captured on video some years ago. Liz, a fifth-grade teacher, gave her students two-digit multiplication problems—12 × 29 and 36 × 17— and asked them to come up with strategies other than the conventional algorithm to perform the calculation. For 12 × 29, Jemea thought about twelve 30s and then subtracted 1 for each of 12 groups. 360 – 12 = 348. For 36 × 17, Duane thought of 36 bowls, each holding 17 cotton balls. Ten bowls hold 170 cotton balls, and there are...