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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 341 · 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. 1.68 + 9 =
  2. 2.46 − 29 =
  3. 3.66 + 29 =
  4. 4.30 + 29 =
  5. 5.76 + 19 =
  6. 6.57 + 9 =
  7. 7.54 + 19 =
  8. 8.64 − 29 =
  9. 9.362 − 99 =
  10. 10.425 + 99 =
  11. 11.50 − 9 =
  12. 12.83 − 19 =
  13. 13.65 + 19 =
  14. 14.36 + 29 =
  15. 15.685 + 99 =
  16. 16.36 + 19 =
  17. 17.784 − 99 =
  18. 18.12 + 9 =
  19. 19.64 + 29 =
  20. 20.80 + 9 =
  21. 21.35 + 9 =
  22. 22.321 + 99 =
  23. 23.21 + 9 =
  24. 24.845 − 99 =
  25. 25.100 − 29 =
  26. 26.35 + 29 =
  27. 27.60 + 29 =
  28. 28.56 + 19 =
  29. 29.577 + 99 =
  30. 30.57 − 9 =
  31. 31.17 + 9 =
  32. 32.33 − 29 =
  33. 33.49 − 9 =
  34. 34.19 + 19 =
  35. 35.311 − 99 =
  36. 36.32 + 9 =
  37. 37.39 − 29 =
  38. 38.42 + 29 =
  39. 39.523 + 99 =
  40. 40.417 + 99 =

Answer key

  1. 77
  2. 17
  3. 95
  4. 59
  5. 95
  6. 66
  7. 73
  8. 35
  9. 263
  10. 524
  11. 41
  12. 64
  13. 84
  14. 65
  15. 784
  16. 55
  17. 685
  18. 21
  19. 93
  20. 89
  21. 44
  22. 420
  23. 30
  24. 746
  25. 71
  26. 64
  27. 89
  28. 75
  29. 676
  30. 48
  31. 26
  32. 4
  33. 40
  34. 38
  35. 212
  36. 41
  37. 10
  38. 71
  39. 622
  40. 516

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