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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 607 · 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. 1.19 + 29 =
  2. 2.40 − 19 =
  3. 3.48 + 9 =
  4. 4.37 − 29 =
  5. 5.43 + 29 =
  6. 6.42 − 9 =
  7. 7.15 + 9 =
  8. 8.22 + 29 =
  9. 9.61 + 19 =
  10. 10.14 + 29 =
  11. 11.60 + 19 =
  12. 12.32 + 9 =
  13. 13.629 − 99 =
  14. 14.42 + 9 =
  15. 15.432 − 99 =
  16. 16.38 − 19 =
  17. 17.57 − 9 =
  18. 18.68 + 29 =
  19. 19.29 + 29 =
  20. 20.61 + 9 =
  21. 21.330 + 99 =
  22. 22.55 + 9 =
  23. 23.18 − 9 =
  24. 24.32 − 9 =
  25. 25.36 + 19 =
  26. 26.71 − 29 =
  27. 27.94 − 29 =
  28. 28.27 − 19 =
  29. 29.26 + 29 =
  30. 30.385 + 99 =
  31. 31.41 + 29 =
  32. 32.64 − 19 =
  33. 33.560 + 99 =
  34. 34.557 + 99 =
  35. 35.66 + 19 =
  36. 36.39 − 9 =
  37. 37.100 − 29 =
  38. 38.422 + 99 =
  39. 39.42 + 29 =
  40. 40.12 + 19 =

Answer key

  1. 48
  2. 21
  3. 57
  4. 8
  5. 72
  6. 33
  7. 24
  8. 51
  9. 80
  10. 43
  11. 79
  12. 41
  13. 530
  14. 51
  15. 333
  16. 19
  17. 48
  18. 97
  19. 58
  20. 70
  21. 429
  22. 64
  23. 9
  24. 23
  25. 55
  26. 42
  27. 65
  28. 8
  29. 55
  30. 484
  31. 70
  32. 45
  33. 659
  34. 656
  35. 85
  36. 30
  37. 71
  38. 521
  39. 71
  40. 31

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