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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 401 · 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. 1.59 + 19 =
  2. 2.37 + 19 =
  3. 3.72 + 9 =
  4. 4.81 − 19 =
  5. 5.617 − 99 =
  6. 6.698 − 99 =
  7. 7.24 − 19 =
  8. 8.62 + 9 =
  9. 9.31 − 19 =
  10. 10.39 + 19 =
  11. 11.48 + 9 =
  12. 12.34 − 9 =
  13. 13.53 − 19 =
  14. 14.48 − 19 =
  15. 15.49 − 29 =
  16. 16.286 − 99 =
  17. 17.491 − 99 =
  18. 18.17 + 19 =
  19. 19.56 + 9 =
  20. 20.17 + 29 =
  21. 21.58 + 9 =
  22. 22.79 + 9 =
  23. 23.35 − 19 =
  24. 24.15 − 9 =
  25. 25.38 + 19 =
  26. 26.35 + 9 =
  27. 27.23 + 9 =
  28. 28.54 + 9 =
  29. 29.76 − 9 =
  30. 30.22 − 9 =
  31. 31.67 + 9 =
  32. 32.109 − 29 =
  33. 33.476 + 99 =
  34. 34.49 − 9 =
  35. 35.517 − 99 =
  36. 36.563 − 99 =
  37. 37.13 + 9 =
  38. 38.46 − 29 =
  39. 39.22 + 9 =
  40. 40.48 − 9 =

Answer key

  1. 78
  2. 56
  3. 81
  4. 62
  5. 518
  6. 599
  7. 5
  8. 71
  9. 12
  10. 58
  11. 57
  12. 25
  13. 34
  14. 29
  15. 20
  16. 187
  17. 392
  18. 36
  19. 65
  20. 46
  21. 67
  22. 88
  23. 16
  24. 6
  25. 57
  26. 44
  27. 32
  28. 63
  29. 67
  30. 13
  31. 76
  32. 80
  33. 575
  34. 40
  35. 418
  36. 464
  37. 22
  38. 17
  39. 31
  40. 39

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