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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 411 · 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. 1.35 + 19 =
  2. 2.482 + 99 =
  3. 3.85 − 19 =
  4. 4.48 − 19 =
  5. 5.60 + 9 =
  6. 6.75 − 9 =
  7. 7.75 + 29 =
  8. 8.784 − 99 =
  9. 9.97 − 29 =
  10. 10.45 + 9 =
  11. 11.201 + 99 =
  12. 12.59 − 29 =
  13. 13.80 − 29 =
  14. 14.61 + 29 =
  15. 15.53 − 19 =
  16. 16.26 + 9 =
  17. 17.36 − 29 =
  18. 18.42 − 29 =
  19. 19.58 + 29 =
  20. 20.75 − 19 =
  21. 21.38 − 29 =
  22. 22.41 + 29 =
  23. 23.528 + 99 =
  24. 24.56 + 9 =
  25. 25.863 − 99 =
  26. 26.69 − 29 =
  27. 27.394 − 99 =
  28. 28.23 + 9 =
  29. 29.67 + 29 =
  30. 30.43 − 19 =
  31. 31.80 + 29 =
  32. 32.65 − 29 =
  33. 33.41 + 9 =
  34. 34.52 + 9 =
  35. 35.24 + 9 =
  36. 36.47 − 29 =
  37. 37.703 + 99 =
  38. 38.68 + 9 =
  39. 39.34 + 29 =
  40. 40.83 − 19 =

Answer key

  1. 54
  2. 581
  3. 66
  4. 29
  5. 69
  6. 66
  7. 104
  8. 685
  9. 68
  10. 54
  11. 300
  12. 30
  13. 51
  14. 90
  15. 34
  16. 35
  17. 7
  18. 13
  19. 87
  20. 56
  21. 9
  22. 70
  23. 627
  24. 65
  25. 764
  26. 40
  27. 295
  28. 32
  29. 96
  30. 24
  31. 109
  32. 36
  33. 50
  34. 61
  35. 33
  36. 18
  37. 802
  38. 77
  39. 63
  40. 64

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