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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 142 · 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. 1.39 + 19 =
  2. 2.25 + 19 =
  3. 3.39 − 29 =
  4. 4.80 + 19 =
  5. 5.67 + 9 =
  6. 6.60 − 9 =
  7. 7.49 + 9 =
  8. 8.33 + 29 =
  9. 9.45 − 19 =
  10. 10.65 + 9 =
  11. 11.42 − 29 =
  12. 12.536 + 99 =
  13. 13.57 − 9 =
  14. 14.52 + 19 =
  15. 15.371 − 99 =
  16. 16.57 + 9 =
  17. 17.76 − 29 =
  18. 18.40 − 19 =
  19. 19.86 − 29 =
  20. 20.28 − 19 =
  21. 21.57 − 19 =
  22. 22.606 + 99 =
  23. 23.827 − 99 =
  24. 24.74 + 19 =
  25. 25.19 + 19 =
  26. 26.85 − 19 =
  27. 27.70 − 9 =
  28. 28.29 + 9 =
  29. 29.25 − 19 =
  30. 30.55 + 19 =
  31. 31.73 − 9 =
  32. 32.412 − 99 =
  33. 33.64 + 19 =
  34. 34.41 + 19 =
  35. 35.50 − 9 =
  36. 36.31 − 9 =
  37. 37.619 − 99 =
  38. 38.608 + 99 =
  39. 39.77 + 9 =
  40. 40.58 − 29 =

Answer key

  1. 58
  2. 44
  3. 10
  4. 99
  5. 76
  6. 51
  7. 58
  8. 62
  9. 26
  10. 74
  11. 13
  12. 635
  13. 48
  14. 71
  15. 272
  16. 66
  17. 47
  18. 21
  19. 57
  20. 9
  21. 38
  22. 705
  23. 728
  24. 93
  25. 38
  26. 66
  27. 61
  28. 38
  29. 6
  30. 74
  31. 64
  32. 313
  33. 83
  34. 60
  35. 41
  36. 22
  37. 520
  38. 707
  39. 86
  40. 29

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