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Objective: To be able to use mental methods of calculation

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 =7.

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Objective: To be able to use mental methods of calculation

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

  2. 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 =7

  3. 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

  4. Pairs of 2-digit numbers 76 + 58 76 + 58 70 + 50 + 6 + 8 76 + 8 + 50 120 + 14 84 + 50 120 + 10 + 4 = 134 = 134

  5. Pairs of 2-digit numbers 76 – 58 76 – 58 76 – 50 – 8 76 – 8 – 50 26 – 8 68 –50 = 18 = 18

  6. 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

  7. Partitioning 426 + 65 = 491 +60 +5 426 486 491

  8. Partitioning and more 14.3 – 5.5 = 8.8 -0.2 -0.3 -5 8.8 9.0 9.3 14.3

  9. 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

  10. Compensating 4.7 + 2.9 = 7.6 +3 -0.1 4.7 7.6 7.7

  11. Compensating 530 - 294 = 236 -300 +6 230 236 530

  12. 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

  13. 3.3 3.3 5.4 5.4 4.2 4.2 6.9 4.9 3.7 2.2 2.2 2.2 2.2 3.7 Find the perimeter of these shapes ANSWERS: 19.9 17.7 16.2

  14. Multiplication and Division Mental Methods

  15. 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 2so ÷6 is ÷3÷2

  16. 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

  17. Use partitioning 7.3 x 11 = 7.3 x 10 + 7.3 x 1 = 73 + 7.3 = 80.3 330 ÷ 14 300÷ 14 = 21 r 6 30÷ 14 = 2 r 2 330÷ 14 = 23 r 8

  18. Work out these: 3.4 x 21 6.3 x 33 9.2 x 52 140 ÷ 16 150 ÷ 14 264 ÷ 13 =3.4x20+3.4x1=68 +3.4=71.4 =6.3x30+6.3x3 =189+18.9=207.9 =9.2x50+9.2x2=460+18.4=478.4 =100÷16=6r4, 40÷16=2r8 8r12 =100÷14=7r2, 50÷14=3r8 10r10 =200÷13=15r5, 64÷13=4r12 19r17 = 20r4

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

  20. 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

  21. 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 4 1 2 5 1 2 4 2 5 1 3 2 4 1 3 2

  22. 1 12 8 4 6 2 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 4 x 12 x 1 = 48 1 x 8 x 6 = 48 4 x 2 x 6 = 48

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