•Reordering
Year 5 12 + 17 + 8 + 3 reordered= 12 + 8 + 17 + 3
25 + 36 + 75 reordered= 25 + 75 + 36
58 + 47 – 38 reordered= 58 – 38 + 47
200 + 567 reordered=567 + 200
1.7 + 2.8 + 0.3 1.7 + 0.3 + 2.8
Year 6 3 + 8 + 7 + 6 + 2 reordered=3 + 7 + 8 + 2 + 6
34 + 27 + 46 reordered=34 + 46 + 27
180 + 650 650 + 180 (thinking of 180 as 150 + 30)
1.7 + 2.8 + 0.3 reordered= 1.7 + 0.3 + 2.8
4.7 + 5.6 – 0.7 reordered=4.7 – 0.7 + 5.6 = 4 + 5.6
• Partitioning: counting on or back
Year 5 43 + 28 + 51 =40 + 3 + 20 + 8 + 50 + 1 = 40 + 20 + 50 + 3 + 8 + 1
5.6 + 3.7 5.6 + 3 + 0.7 = 8.6 + 0.7 4.7 – 3.5 4.7 – 3 – 0.5
Year 6 540 + 280 =540 + 200 + 80
276 – 153 =276 – 100 – 50 – 3
• Partitioning: bridging a multiple of 10
Year 5 607 – 288 288 + 12 + 300 + 7
6070 – 4987 4987 + 13 + 1000 + 70
Year 6 1.4 + 1.7 or 5.6 – 3.7 =1.4 + 0.6 + 1.1 or 5.6 – 0.6 – 3 – 0.1
0.8 + 0.35 =0.8 + 0.2 + 0.15
8.3 – 2.8= 2.8 + 0.2 + 5.3 or 8.3 – 2.3 – 0.5
• Partitioning: compensating
Year 5 138 + 69= 138 + 70 – 1
405 – 399 =405 – 400 + 1
Year 6 2½ + 1¾= 2½ + 2 – ¼
5.7 + 3.9= 5.7 + 4.0 – 0.1
6.8 – 4.9= 6.8 – 5.0 + 0.1
• Partitioning: using ‘near’ doubles
Year 5 160 + 170 is double 150, then add 10, then add 20 or double 160 and add 10 or double 170 and subtract 10
Year 6 2.5 + 2.6 is double 2.5 and add 0.1 or double 2.6 and subtract 0.1
• Partitioning: bridging through 60 to calculate a time interval
Year 5 What time will it be 26 minutes after 3.30am?
What was the time 33 minutes before 2.15pm?
It is 4.18pm. How many minutes to 5.00pm? 5.26pm?
Year 6 It is 08.35. How many minutes is it to 09.15?
It is 11.45. How many hours and minutes is it to 15.20?
A train leaves London for Leeds at 22.33.
The journey takes 2 hours 47 minutes. What time does the train arrive?