Explain why expanded form is more than just a notation exercise — how does understanding expanded form connect to doing addition with multi-digit numbers?
Think about your answer, then reveal below.
Model answer: Expanded form reveals that multi-digit addition is really place-by-place addition. When you add 234 + 153, you are adding the hundreds (200 + 100 = 300), the tens (30 + 50 = 80), and the ones (4 + 3 = 7) separately, then combining: 300 + 80 + 7 = 387. Every column in the standard addition algorithm corresponds to one position in expanded form.
The column-by-column structure of the standard addition algorithm is directly an application of expanded form: you add the ones column, then the tens column, then the hundreds column — each column corresponds to one addend in the expanded representation. Understanding expanded form prevents students from treating multi-digit numbers as sequences of unrelated digits. It shows that 234 is not 'two, three, four' but 'two hundred plus thirty plus four' — a sum whose parts can be operated on independently and then recombined.