Addition with 3-digit numbers
1 Look at the different methods used to complete the addition 355 + 132. Why is 400 + 100 = 500 a useful estimate?
+100
355 + 132 = 300 + 50 + 5 + 100 + 30 + 2 = 400 + 80 + 7 = 487
+30 +20
487
355
455 485 What is the same and what is different about the methods? What calculation can you use to check?
355 + 132 = 355 + 100 + 30 + 2 = 455 + 30 + 2 = 485 + 2 = 487
2 We can also solve additions using the written column method.
We start by adding the ones: 5 ones + 2 ones = 7 ones 5 tens + 3 tens = 8 tens 3 hundreds + 1 hundred = 4 hundreds
H T O 3 5 5 + 1 3 2 4 8 7
H T
O
+
Which method did you prefer for this calculation? Why?
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04/05/2022 15:49
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