3/8 Estimate answers to calculations A 2-digit number by a single digit Round off each number Column method Then do the calculation 3 8 Check using the inverse 3 x 1 1 4 Example: Estimate 83 – 28 2 80 – 30 = 50 Inverse: 50 + 30 = 80 Grid method 30 8 3 90 24 3/9 Missing number problems 90 + 24 = 114 Fact family for +/- Partitioning method 38 x 3 34 + 23 = 57 57 - 23 = 34 = 30 x3 + 8 x 3 = 90 + 24 23 + 34 = 57 57 – 34 = 23 = 114 3/12 Multiply & divide 3/10 Know the 3, 4 and 8 times tables Look for connections between two sums Remember the fact family for x/÷ 1 x 3 = 3 1 x 4 = 4 1 x 8 = 8 2 x 3 = 6 2 x 4 = 8 2 x 8 = 16 3 x 3 = 9 3 x 4 = 12 3 x 8 = 24 Example: 6 x 4 = 24 So 60 x 4 = 240 So 240 ÷ 4 = 60 4 x 3 = 12 4 x 4 = 16 4 x 8 = 32 5 x 3 = 15 5 x 4 = 20 5 x 8 = 40 6 x 3 = 18 6 x 4 = 24 6 x 8 = 48 Example: 9 x 8 = 72 So 18 x 8 = 144 7 x 3 = 21 7 x 4 = 28 7 x 8 = 56 So 144 ÷ 8 = 18 8 x 3 = 24 8 x 4 = 32 8 x 8 = 64 9 x 3 = 27 9 x 4 = 36 9 x 8 = 72 10 x 3 = 30 10 x 4 = 40 10 x 8 = 80 11 x 3 = 33 11 x 4 = 44 11 x 8 = 88 12 x 3 = 36 12 x 4 = 48 12 x 8 = 96 3/13 Tenths Fact family for x/÷ . 9 x 8 = 72 72 ÷ 9 = 8 units tens tenths 8 x 9 = 72 72 ÷ 8 = 9 8 2 6 This represents 6 tenths = Counting in tenths (continued) 3/11 Multiply & divide
3/8 Estimate answers to calculations Round off each number Then do the calculation Check using the inverse Example: Estimate 83 – 28 80 – 30 = 50 Inverse: 50 + 30 = 80 3/9 Missing number problems Fact family for +/- 34 + 23 = 57 57 - 23 = 34 23 + 34 = 57 57 – 34 = 23 3/10 Know the 3, 4 and 8 times tables 1 x 3 = 3 2 x 3 = 6 3 x 3 = 9 4 x 3 = 12 5 x 3 = 15 6 x 3 = 18 7 x 3 = 21 8 x 3 = 24 9 x 3 = 27 10 x 3 = 30 11 x 3 = 33 12 x 3 = 36 1 x 4 = 4 2 x 4 = 8 3 x 4 = 12 4 x 4 = 16 5 x 4 = 20 6 x 4 = 24 7 x 4 = 28 8 x 4 = 32 9 x 4 = 36 10 x 4 = 40 11 x 4 = 44 12 x 4 = 48 1 x 8 = 8 2 x 8 = 16 3 x 8 = 24 4 x 8 = 32 5 x 8 = 40 6 x 8 = 48 7 x 8 = 56 8 x 8 = 64 9 x 8 = 72 10 x 8 = 80 11 x 8 = 88 12 x 8 = 96 Fact family for x/÷ 9 x 8 = 72 72 ÷ 9 = 8 8 x 9 = 72 72 ÷ 8 = 9 3/11 Multiply & divide A 2-digit number by a single digit Column method 3 8 3 x 1 1 4 2 Grid method 30 8 3 90 24 90 + 24 = 114 Partitioning method 38 x 3 = 30 x3 + 8 x 3 = 90 + 24 = 114 3/12 Multiply & divide Look for connections between two sums Remember the fact family for x/÷ Example: 6 x 4 = 24 So 60 x 4 = 240 So 240 ÷ 4 = 60 Example: 9 x 8 = 72 So 18 x 8 = 144 So 144 ÷ 8 = 18 3/13 Tenths tens units . tenths 8 2 6 This represents 6 tenths = Counting in tenths (continued)