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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 236 · 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. 1.96 − 19 =
  2. 2.143 + 99 =
  3. 3.466 − 99 =
  4. 4.55 + 9 =
  5. 5.176 − 99 =
  6. 6.21 + 9 =
  7. 7.67 − 19 =
  8. 8.71 + 19 =
  9. 9.195 + 99 =
  10. 10.18 + 19 =
  11. 11.260 − 99 =
  12. 12.12 + 9 =
  13. 13.94 − 29 =
  14. 14.64 − 29 =
  15. 15.64 + 29 =
  16. 16.61 + 29 =
  17. 17.229 + 99 =
  18. 18.32 − 9 =
  19. 19.108 − 29 =
  20. 20.30 + 9 =
  21. 21.43 − 19 =
  22. 22.74 + 9 =
  23. 23.424 + 99 =
  24. 24.76 − 9 =
  25. 25.66 − 19 =
  26. 26.44 − 9 =
  27. 27.93 − 29 =
  28. 28.15 − 9 =
  29. 29.67 + 9 =
  30. 30.62 + 19 =
  31. 31.74 − 29 =
  32. 32.58 + 29 =
  33. 33.442 − 99 =
  34. 34.58 − 9 =
  35. 35.80 − 9 =
  36. 36.54 − 9 =
  37. 37.188 − 99 =
  38. 38.20 + 29 =
  39. 39.72 + 29 =
  40. 40.24 + 29 =

Answer key

  1. 77
  2. 242
  3. 367
  4. 64
  5. 77
  6. 30
  7. 48
  8. 90
  9. 294
  10. 37
  11. 161
  12. 21
  13. 65
  14. 35
  15. 93
  16. 90
  17. 328
  18. 23
  19. 79
  20. 39
  21. 24
  22. 83
  23. 523
  24. 67
  25. 47
  26. 35
  27. 64
  28. 6
  29. 76
  30. 81
  31. 45
  32. 87
  33. 343
  34. 49
  35. 71
  36. 45
  37. 89
  38. 49
  39. 101
  40. 53

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