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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 78 · 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. 1.50 + 9 =
  2. 2.72 − 19 =
  3. 3.55 − 9 =
  4. 4.56 + 29 =
  5. 5.586 − 99 =
  6. 6.168 + 99 =
  7. 7.13 + 9 =
  8. 8.594 + 99 =
  9. 9.15 + 9 =
  10. 10.27 + 9 =
  11. 11.70 − 29 =
  12. 12.16 + 29 =
  13. 13.845 − 99 =
  14. 14.50 + 19 =
  15. 15.49 − 29 =
  16. 16.71 + 29 =
  17. 17.73 + 9 =
  18. 18.38 − 9 =
  19. 19.770 + 99 =
  20. 20.560 − 99 =
  21. 21.36 − 19 =
  22. 22.20 + 19 =
  23. 23.55 + 19 =
  24. 24.68 − 29 =
  25. 25.62 + 29 =
  26. 26.47 + 29 =
  27. 27.78 − 19 =
  28. 28.28 + 29 =
  29. 29.14 + 19 =
  30. 30.47 − 19 =
  31. 31.51 − 9 =
  32. 32.382 − 99 =
  33. 33.26 + 29 =
  34. 34.22 + 19 =
  35. 35.71 + 9 =
  36. 36.76 − 19 =
  37. 37.76 − 9 =
  38. 38.686 − 99 =
  39. 39.71 − 9 =
  40. 40.14 − 9 =

Answer key

  1. 59
  2. 53
  3. 46
  4. 85
  5. 487
  6. 267
  7. 22
  8. 693
  9. 24
  10. 36
  11. 41
  12. 45
  13. 746
  14. 69
  15. 20
  16. 100
  17. 82
  18. 29
  19. 869
  20. 461
  21. 17
  22. 39
  23. 74
  24. 39
  25. 91
  26. 76
  27. 59
  28. 57
  29. 33
  30. 28
  31. 42
  32. 283
  33. 55
  34. 41
  35. 80
  36. 57
  37. 67
  38. 587
  39. 62
  40. 5

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