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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 569 · 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. 1.173 + 99 =
  2. 2.79 − 9 =
  3. 3.16 + 29 =
  4. 4.46 − 19 =
  5. 5.98 − 29 =
  6. 6.78 + 19 =
  7. 7.51 + 9 =
  8. 8.21 + 29 =
  9. 9.76 + 9 =
  10. 10.22 − 9 =
  11. 11.100 − 29 =
  12. 12.23 + 29 =
  13. 13.674 − 99 =
  14. 14.12 − 9 =
  15. 15.745 + 99 =
  16. 16.555 + 99 =
  17. 17.53 + 19 =
  18. 18.51 − 9 =
  19. 19.80 + 19 =
  20. 20.455 − 99 =
  21. 21.44 + 9 =
  22. 22.797 + 99 =
  23. 23.27 + 19 =
  24. 24.151 + 99 =
  25. 25.861 − 99 =
  26. 26.80 + 9 =
  27. 27.76 − 19 =
  28. 28.52 + 29 =
  29. 29.63 + 19 =
  30. 30.58 − 9 =
  31. 31.60 + 9 =
  32. 32.49 + 19 =
  33. 33.708 − 99 =
  34. 34.79 − 19 =
  35. 35.95 − 29 =
  36. 36.43 + 19 =
  37. 37.16 + 9 =
  38. 38.20 + 9 =
  39. 39.67 + 29 =
  40. 40.58 − 19 =

Answer key

  1. 272
  2. 70
  3. 45
  4. 27
  5. 69
  6. 97
  7. 60
  8. 50
  9. 85
  10. 13
  11. 71
  12. 52
  13. 575
  14. 3
  15. 844
  16. 654
  17. 72
  18. 42
  19. 99
  20. 356
  21. 53
  22. 896
  23. 46
  24. 250
  25. 762
  26. 89
  27. 57
  28. 81
  29. 82
  30. 49
  31. 69
  32. 68
  33. 609
  34. 60
  35. 66
  36. 62
  37. 25
  38. 29
  39. 96
  40. 39

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