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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 961 · 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. 1.24 + 9 =
  2. 2.61 − 9 =
  3. 3.214 − 99 =
  4. 4.32 + 9 =
  5. 5.81 − 9 =
  6. 6.17 + 9 =
  7. 7.73 − 19 =
  8. 8.19 + 19 =
  9. 9.48 + 29 =
  10. 10.61 + 29 =
  11. 11.57 − 29 =
  12. 12.44 − 19 =
  13. 13.88 − 29 =
  14. 14.66 + 29 =
  15. 15.87 − 9 =
  16. 16.73 + 29 =
  17. 17.493 − 99 =
  18. 18.49 + 19 =
  19. 19.34 − 19 =
  20. 20.78 + 29 =
  21. 21.35 + 29 =
  22. 22.40 − 19 =
  23. 23.30 − 9 =
  24. 24.104 − 29 =
  25. 25.562 − 99 =
  26. 26.74 − 29 =
  27. 27.74 + 29 =
  28. 28.72 − 9 =
  29. 29.75 + 29 =
  30. 30.69 + 29 =
  31. 31.12 − 9 =
  32. 32.41 + 9 =
  33. 33.71 + 29 =
  34. 34.52 − 9 =
  35. 35.49 − 9 =
  36. 36.57 − 9 =
  37. 37.677 + 99 =
  38. 38.48 + 9 =
  39. 39.36 + 9 =
  40. 40.634 + 99 =

Answer key

  1. 33
  2. 52
  3. 115
  4. 41
  5. 72
  6. 26
  7. 54
  8. 38
  9. 77
  10. 90
  11. 28
  12. 25
  13. 59
  14. 95
  15. 78
  16. 102
  17. 394
  18. 68
  19. 15
  20. 107
  21. 64
  22. 21
  23. 21
  24. 75
  25. 463
  26. 45
  27. 103
  28. 63
  29. 104
  30. 98
  31. 3
  32. 50
  33. 100
  34. 43
  35. 40
  36. 48
  37. 776
  38. 57
  39. 45
  40. 733

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