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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 564 · 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. 1.37 − 29 =
  2. 2.731 − 99 =
  3. 3.50 + 9 =
  4. 4.41 − 9 =
  5. 5.15 + 29 =
  6. 6.18 + 9 =
  7. 7.54 − 9 =
  8. 8.24 − 9 =
  9. 9.40 + 9 =
  10. 10.75 − 19 =
  11. 11.23 − 19 =
  12. 12.172 + 99 =
  13. 13.74 + 29 =
  14. 14.775 + 99 =
  15. 15.29 + 29 =
  16. 16.53 + 9 =
  17. 17.78 + 19 =
  18. 18.25 + 29 =
  19. 19.21 + 9 =
  20. 20.66 + 9 =
  21. 21.277 + 99 =
  22. 22.78 + 29 =
  23. 23.502 + 99 =
  24. 24.80 + 19 =
  25. 25.36 − 19 =
  26. 26.27 − 9 =
  27. 27.62 + 9 =
  28. 28.41 + 29 =
  29. 29.46 − 19 =
  30. 30.219 + 99 =
  31. 31.16 + 29 =
  32. 32.14 − 9 =
  33. 33.52 − 29 =
  34. 34.70 + 29 =
  35. 35.17 + 9 =
  36. 36.35 + 9 =
  37. 37.47 − 29 =
  38. 38.52 − 19 =
  39. 39.27 + 29 =
  40. 40.61 + 29 =

Answer key

  1. 8
  2. 632
  3. 59
  4. 32
  5. 44
  6. 27
  7. 45
  8. 15
  9. 49
  10. 56
  11. 4
  12. 271
  13. 103
  14. 874
  15. 58
  16. 62
  17. 97
  18. 54
  19. 30
  20. 75
  21. 376
  22. 107
  23. 601
  24. 99
  25. 17
  26. 18
  27. 71
  28. 70
  29. 27
  30. 318
  31. 45
  32. 5
  33. 23
  34. 99
  35. 26
  36. 44
  37. 18
  38. 33
  39. 56
  40. 90

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