- Chinese method is really just rote learning.
- Grid method is promoted in primary schools.
- Good because it can be introduced by counting the number of squares, so promotes understanding of the size of a multiplication problem.
- For example: 14 x 12
Total = 100 + 40 + 20 + 8 = 168
- You can also expand brackets using the grid method:
- 32 x 41 is equivalent to (30 + 2) (40 + 1)
- (x + 2)(x + 1)
So the answer is x2 + 3x + 2
- This can be extended to negative numbers, but you need to make clear that the operations are the same.
- N.B. Students will tend to say 2x rather than x2. Scaffold using: 2×2=22, 3×3=32, 4×4=42
- You can also use the grid method to explore the difference of two squares (but its even better using geogebra!)