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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 293 · 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. 1.33 − 9 =
  2. 2.68 − 29 =
  3. 3.44 + 9 =
  4. 4.43 + 19 =
  5. 5.32 + 9 =
  6. 6.69 + 19 =
  7. 7.590 − 99 =
  8. 8.86 − 29 =
  9. 9.108 − 29 =
  10. 10.45 + 29 =
  11. 11.50 + 29 =
  12. 12.195 + 99 =
  13. 13.244 + 99 =
  14. 14.66 + 9 =
  15. 15.74 + 19 =
  16. 16.231 − 99 =
  17. 17.74 − 29 =
  18. 18.87 − 9 =
  19. 19.19 + 19 =
  20. 20.16 + 19 =
  21. 21.309 − 99 =
  22. 22.54 − 29 =
  23. 23.33 + 19 =
  24. 24.35 − 29 =
  25. 25.61 + 19 =
  26. 26.12 − 9 =
  27. 27.274 + 99 =
  28. 28.202 + 99 =
  29. 29.72 + 19 =
  30. 30.51 + 9 =
  31. 31.31 − 19 =
  32. 32.20 + 29 =
  33. 33.655 + 99 =
  34. 34.100 − 29 =
  35. 35.24 + 29 =
  36. 36.77 − 9 =
  37. 37.65 + 19 =
  38. 38.607 + 99 =
  39. 39.250 + 99 =
  40. 40.41 + 29 =

Answer key

  1. 24
  2. 39
  3. 53
  4. 62
  5. 41
  6. 88
  7. 491
  8. 57
  9. 79
  10. 74
  11. 79
  12. 294
  13. 343
  14. 75
  15. 93
  16. 132
  17. 45
  18. 78
  19. 38
  20. 35
  21. 210
  22. 25
  23. 52
  24. 6
  25. 80
  26. 3
  27. 373
  28. 301
  29. 91
  30. 60
  31. 12
  32. 49
  33. 754
  34. 71
  35. 53
  36. 68
  37. 84
  38. 706
  39. 349
  40. 70

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