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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 54 · 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. 1.88 − 19 =
  2. 2.479 + 99 =
  3. 3.57 + 9 =
  4. 4.75 + 19 =
  5. 5.29 + 9 =
  6. 6.16 − 9 =
  7. 7.26 − 9 =
  8. 8.68 − 19 =
  9. 9.54 − 29 =
  10. 10.58 + 9 =
  11. 11.12 + 29 =
  12. 12.36 + 19 =
  13. 13.52 + 19 =
  14. 14.32 + 9 =
  15. 15.68 + 19 =
  16. 16.93 − 29 =
  17. 17.495 + 99 =
  18. 18.58 − 19 =
  19. 19.63 + 9 =
  20. 20.40 − 9 =
  21. 21.60 − 19 =
  22. 22.34 + 19 =
  23. 23.14 − 9 =
  24. 24.45 − 19 =
  25. 25.30 + 19 =
  26. 26.66 − 9 =
  27. 27.96 − 29 =
  28. 28.39 + 19 =
  29. 29.39 − 9 =
  30. 30.33 + 9 =
  31. 31.51 − 29 =
  32. 32.665 + 99 =
  33. 33.38 + 19 =
  34. 34.22 − 9 =
  35. 35.22 + 9 =
  36. 36.673 + 99 =
  37. 37.94 − 29 =
  38. 38.467 + 99 =
  39. 39.72 + 19 =
  40. 40.26 + 29 =

Answer key

  1. 69
  2. 578
  3. 66
  4. 94
  5. 38
  6. 7
  7. 17
  8. 49
  9. 25
  10. 67
  11. 41
  12. 55
  13. 71
  14. 41
  15. 87
  16. 64
  17. 594
  18. 39
  19. 72
  20. 31
  21. 41
  22. 53
  23. 5
  24. 26
  25. 49
  26. 57
  27. 67
  28. 58
  29. 30
  30. 42
  31. 22
  32. 764
  33. 57
  34. 13
  35. 31
  36. 772
  37. 65
  38. 566
  39. 91
  40. 55

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