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Published byTrever Beatson Modified over 3 years ago

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Objective: To be able to use mental methods of calculation

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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

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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

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

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

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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

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Partitioning 426 + 65 426486491 +60+5 = 491

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

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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

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Compensating 4.7 + 2.9 4.77.67.7 +3-0.1 = 7.6

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Compensating 530 - 294 230236530 -300 +6 = 236

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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

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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

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Multiplication and Division Mental Methods

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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

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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

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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

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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

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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

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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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© T Madas. 6 m 8 m Finding the hypotenuse x 6262 + 8 2 = x2= x2 36 + 64 = x2= x2 100 = x2= x2 = x= x = x= x 10 x = 10 12 m 13 m Finding one of the shorter.

© T Madas. 6 m 8 m Finding the hypotenuse x 6262 + 8 2 = x2= x2 36 + 64 = x2= x2 100 = x2= x2 = x= x = x= x 10 x = 10 12 m 13 m Finding one of the shorter.

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