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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 428 · 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. 1.543 + 99 =
  2. 2.70 + 19 =
  3. 3.121 + 99 =
  4. 4.233 + 99 =
  5. 5.46 + 29 =
  6. 6.14 + 19 =
  7. 7.541 − 99 =
  8. 8.156 − 99 =
  9. 9.32 + 9 =
  10. 10.637 + 99 =
  11. 11.698 − 99 =
  12. 12.25 − 9 =
  13. 13.48 − 9 =
  14. 14.69 + 9 =
  15. 15.83 − 19 =
  16. 16.65 + 29 =
  17. 17.62 − 29 =
  18. 18.70 + 29 =
  19. 19.74 + 19 =
  20. 20.68 − 19 =
  21. 21.50 + 9 =
  22. 22.44 − 9 =
  23. 23.844 − 99 =
  24. 24.54 + 19 =
  25. 25.63 + 9 =
  26. 26.20 + 19 =
  27. 27.75 + 19 =
  28. 28.52 − 19 =
  29. 29.59 − 29 =
  30. 30.800 − 99 =
  31. 31.19 + 29 =
  32. 32.306 + 99 =
  33. 33.428 + 99 =
  34. 34.102 − 29 =
  35. 35.34 + 9 =
  36. 36.40 + 29 =
  37. 37.34 + 19 =
  38. 38.767 − 99 =
  39. 39.25 − 19 =
  40. 40.103 − 29 =

Answer key

  1. 642
  2. 89
  3. 220
  4. 332
  5. 75
  6. 33
  7. 442
  8. 57
  9. 41
  10. 736
  11. 599
  12. 16
  13. 39
  14. 78
  15. 64
  16. 94
  17. 33
  18. 99
  19. 93
  20. 49
  21. 59
  22. 35
  23. 745
  24. 73
  25. 72
  26. 39
  27. 94
  28. 33
  29. 30
  30. 701
  31. 48
  32. 405
  33. 527
  34. 73
  35. 43
  36. 69
  37. 53
  38. 668
  39. 6
  40. 74

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