面积与乘法分配律
Area and the distributive property
用密铺（平铺）来展示乘法分配律：边长分别为 a 和 (b+c) 的长方形面积等于 a×b + a×c；用面积模型表示乘法分配律。
Use tiling to demonstrate the distributive property: the area of a rectangle with sides a and (b+c) equals a×b + a×c; use area models to represent the distributive property
学习证据 / Evidence
- 铺满一个 3×(4+2) 的长方形，并展示它可以分解成 3×4 和 3×2 两部分。
- 用面积模型计算 6×13，得到 6×10 + 6×3。
- 画一个面积模型表示 5×(7+3) = 5×7 + 5×3。
- Tile a 3×(4+2) rectangle and show it decomposes into 3×4 and 3×2
- Use an area model to compute 6×13 as 6×10 + 6×3
- Draw an area model showing 5×(7+3) = 5×7 + 5×3
评估问题 / Assessment
如果{{name}}想把 6 × 13 拆成 6 × 10 和 6 × 3 来算，他能画一个分成两部分的长方形来说明这种方法为什么成立吗？
If {{name}} wants to work out 6 × 13 by splitting it into 6 × 10 and 6 × 3, can they draw a rectangle divided into two parts to show why that method works?