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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 2 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.56 − 9 =
  2. 2.13 + 29 =
  3. 3.61 − 9 =
  4. 4.12 + 9 =
  5. 5.763 − 99 =
  6. 6.90 − 19 =
  7. 7.279 − 99 =
  8. 8.33 + 9 =
  9. 9.105 − 29 =
  10. 10.265 − 99 =
  11. 11.22 − 9 =
  12. 12.19 − 9 =
  13. 13.511 + 99 =
  14. 14.275 + 99 =
  15. 15.24 + 19 =
  16. 16.87 − 29 =
  17. 17.330 − 99 =
  18. 18.287 + 99 =
  19. 19.36 + 9 =
  20. 20.83 − 19 =
  21. 21.502 + 99 =
  22. 22.72 − 9 =
  23. 23.46 − 9 =
  24. 24.66 + 19 =
  25. 25.610 − 99 =
  26. 26.48 − 9 =
  27. 27.21 − 9 =
  28. 28.57 + 9 =
  29. 29.54 − 29 =
  30. 30.323 − 99 =
  31. 31.63 − 9 =
  32. 32.53 + 29 =
  33. 33.169 + 99 =
  34. 34.44 + 19 =
  35. 35.36 − 19 =
  36. 36.26 − 9 =
  37. 37.58 + 19 =
  38. 38.30 − 9 =
  39. 39.33 + 19 =
  40. 40.25 − 19 =

Answer key

  1. 47
  2. 42
  3. 52
  4. 21
  5. 664
  6. 71
  7. 180
  8. 42
  9. 76
  10. 166
  11. 13
  12. 10
  13. 610
  14. 374
  15. 43
  16. 58
  17. 231
  18. 386
  19. 45
  20. 64
  21. 601
  22. 63
  23. 37
  24. 85
  25. 511
  26. 39
  27. 12
  28. 66
  29. 25
  30. 224
  31. 54
  32. 82
  33. 268
  34. 63
  35. 17
  36. 17
  37. 77
  38. 21
  39. 52
  40. 6

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