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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 343 · 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. 1.58 − 9 =
  2. 2.35 − 19 =
  3. 3.30 + 9 =
  4. 4.402 − 99 =
  5. 5.108 − 29 =
  6. 6.89 − 29 =
  7. 7.38 + 9 =
  8. 8.76 + 9 =
  9. 9.861 − 99 =
  10. 10.53 − 19 =
  11. 11.52 − 29 =
  12. 12.36 + 19 =
  13. 13.69 − 29 =
  14. 14.26 − 19 =
  15. 15.170 − 99 =
  16. 16.455 − 99 =
  17. 17.76 − 19 =
  18. 18.754 + 99 =
  19. 19.721 + 99 =
  20. 20.56 + 19 =
  21. 21.270 + 99 =
  22. 22.104 − 29 =
  23. 23.47 + 9 =
  24. 24.621 − 99 =
  25. 25.36 − 19 =
  26. 26.295 + 99 =
  27. 27.57 − 19 =
  28. 28.23 − 19 =
  29. 29.56 − 29 =
  30. 30.63 − 9 =
  31. 31.70 − 19 =
  32. 32.79 + 19 =
  33. 33.23 + 9 =
  34. 34.48 + 9 =
  35. 35.746 − 99 =
  36. 36.42 + 29 =
  37. 37.68 − 29 =
  38. 38.33 − 19 =
  39. 39.730 + 99 =
  40. 40.33 + 9 =

Answer key

  1. 49
  2. 16
  3. 39
  4. 303
  5. 79
  6. 60
  7. 47
  8. 85
  9. 762
  10. 34
  11. 23
  12. 55
  13. 40
  14. 7
  15. 71
  16. 356
  17. 57
  18. 853
  19. 820
  20. 75
  21. 369
  22. 75
  23. 56
  24. 522
  25. 17
  26. 394
  27. 38
  28. 4
  29. 27
  30. 54
  31. 51
  32. 98
  33. 32
  34. 57
  35. 647
  36. 71
  37. 39
  38. 14
  39. 829
  40. 42

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