# Objective: To be able to use mental methods of calculation.

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Objective: To be able to use mental methods of calculation

Add and subtract small numbers 4 + 8 + 12 + 6 + 13 7 – 2 + 13 – 8 + 5 5 – 9 + 15 – 1 – 4 7 – 1 + 13 – 9 + 3 10 – 6 + 5 – 4 + 7 9 – 5 + 6 – 2 – 1 13 – 6 + 7 – 3 – 4 =43 =15 =6 =13 =12 =7

Add and subtract multiples of 10 20 + 80 + 10 + 30 60 – 40 + 20 – 10 90 – 20 + 30 – 50 30 + 20 – 10 + 30 40 – 20 + 70 + 20 50 – 30 + 20 – 10 50 – 20 + 40 – 10 =140 =30 =50 =70 =110 =30 =60

Pairs of 2-digit numbers 76 + 58 + 6 + 870 + 50 120+ 14 120 + 10 + 4 = 134 76 + 58 + 5076 + 8 84+ 50 = 134

Pairs of 2-digit numbers 76 – 58 – 876 – 50 26– 8 = 18 76 – 58 – 5076 – 8 68– 50 = 18

Pairs of 2-digit numbers 24 + 81 43 + 17 37 + 55 72 + 19 86 – 23 75 – 32 89 + 44 74 - 28 =105 =60 =92 =91 =63 =43 =133 =46

Partitioning 426 + 65 426486491 +60+5 = 491

Partitioning and more 14.3 – 5.5 8.89.314.3 -0.3-5 = 8.8 9.0 -0.2

Work out these: 155 + 36 257 + 65 5.7 + 5.6 88 + 37 46 – 28 96 – 47 7.3 – 3.6 12.4 – 8.5 =191 =322 =11.3 =125 =18 =49 =3.7 =3.9

Compensating 4.7 + 2.9 4.77.67.7 +3-0.1 = 7.6

Compensating 530 - 294 230236530 -300 +6 = 236

Work out these: 235 + 39 167 + 28 7.7 + 4.9 48 + 59 66 – 19 76 – 58 9.3 – 6.9 32.4 – 7.8 =274 =195 =12.6 =107 =47 =18 =2.4 =24.6

Find the perimeter of these shapes 3.3 4.2 4.9 4.2 5.4 6.9 3.7 2.2 ANSWERS: 19.9 17.7 16.2

Multiplication and Division Mental Methods

Use factors 3.2 x 30 3.2 x 10 = 32 32 x 3 = 96 156 ÷ 6 156 ÷ 3 = 52 52 ÷ 2 = 26 30 = 10 x 3 6 = 3 x 2 so ÷6 is ÷3÷2

Work out these: 2.2 x 30 5.2 x 40 6.1 x 12 189 ÷ 90 350 ÷ 14 666 ÷ 18 =2.2 x10 x3 = 66 =5.2 x10 x4 = 208 =6.1 x6 x2=36.6 x2=73.2 =189 ÷9 ÷10=21 ÷10=2.1 =350 ÷7 ÷2 = 50 ÷2 = 25 =666 ÷6 ÷3 = 111 ÷3=37

Double and Halve 6 x 4.5 = 3 x 9 halve one number, double the other = 27 12 x 7.5 = 6 x 15 halve one number, double the other = 3 x 30 halve one number, double the other = 90

Work out these: 30 x 2.5 48 x 1.25 64 x 0.125 = 15 x 5 = 75 = 24 x 2.5 = 12 x 5 = 60 = 32 x 0.25 =16 x 0.5 =8 x 1 = 8

Choose from 1, 2, 3, 4, 5 (use each number no more than once each) a) □ - □ + □ = 5 b) □ + □ - □ = 4 c) □ x □ - □ = 3 d) (□ + □) ÷ □ = 2 e) (□ + □) ÷ (□ + □) = 1 412 512 425 132 4132

Use each of 1, 2, 4, 6, 8, 12 once each so that the product of the number on each side of the triangle is 48 1 12 4 2 6 8 1 x 8 x 6 = 48 4 x 2 x 6 = 48 4 x 12 x 1 = 48

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