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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 112 · 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. 1.81 − 29 =
  2. 2.25 − 19 =
  3. 3.15 − 9 =
  4. 4.314 + 99 =
  5. 5.29 − 19 =
  6. 6.63 + 29 =
  7. 7.23 − 19 =
  8. 8.108 − 29 =
  9. 9.33 − 19 =
  10. 10.89 − 29 =
  11. 11.39 − 9 =
  12. 12.53 + 19 =
  13. 13.23 + 9 =
  14. 14.24 − 9 =
  15. 15.22 + 9 =
  16. 16.763 + 99 =
  17. 17.13 + 9 =
  18. 18.31 + 9 =
  19. 19.45 + 9 =
  20. 20.12 − 9 =
  21. 21.39 + 9 =
  22. 22.733 − 99 =
  23. 23.65 − 9 =
  24. 24.321 + 99 =
  25. 25.44 − 19 =
  26. 26.13 + 19 =
  27. 27.262 + 99 =
  28. 28.34 + 29 =
  29. 29.12 + 9 =
  30. 30.40 − 19 =
  31. 31.489 + 99 =
  32. 32.71 + 19 =
  33. 33.71 − 19 =
  34. 34.66 + 29 =
  35. 35.17 − 9 =
  36. 36.58 − 19 =
  37. 37.54 + 9 =
  38. 38.384 + 99 =
  39. 39.70 + 19 =
  40. 40.27 + 29 =

Answer key

  1. 52
  2. 6
  3. 6
  4. 413
  5. 10
  6. 92
  7. 4
  8. 79
  9. 14
  10. 60
  11. 30
  12. 72
  13. 32
  14. 15
  15. 31
  16. 862
  17. 22
  18. 40
  19. 54
  20. 3
  21. 48
  22. 634
  23. 56
  24. 420
  25. 25
  26. 32
  27. 361
  28. 63
  29. 21
  30. 21
  31. 588
  32. 90
  33. 52
  34. 95
  35. 8
  36. 39
  37. 63
  38. 483
  39. 89
  40. 56

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