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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 690 · 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. 1.26 + 9 =
  2. 2.21 − 9 =
  3. 3.25 + 9 =
  4. 4.611 + 99 =
  5. 5.41 + 29 =
  6. 6.28 + 29 =
  7. 7.169 + 99 =
  8. 8.719 − 99 =
  9. 9.57 + 9 =
  10. 10.382 − 99 =
  11. 11.44 + 19 =
  12. 12.77 − 29 =
  13. 13.38 + 19 =
  14. 14.54 − 29 =
  15. 15.59 + 9 =
  16. 16.80 − 9 =
  17. 17.13 + 9 =
  18. 18.23 + 9 =
  19. 19.309 + 99 =
  20. 20.731 + 99 =
  21. 21.48 + 19 =
  22. 22.35 − 29 =
  23. 23.12 + 19 =
  24. 24.69 − 19 =
  25. 25.41 + 9 =
  26. 26.49 + 9 =
  27. 27.47 − 29 =
  28. 28.40 − 29 =
  29. 29.168 − 99 =
  30. 30.24 − 9 =
  31. 31.71 + 19 =
  32. 32.749 − 99 =
  33. 33.20 + 29 =
  34. 34.48 + 9 =
  35. 35.370 + 99 =
  36. 36.45 − 9 =
  37. 37.57 + 19 =
  38. 38.62 + 9 =
  39. 39.196 + 99 =
  40. 40.61 + 9 =

Answer key

  1. 35
  2. 12
  3. 34
  4. 710
  5. 70
  6. 57
  7. 268
  8. 620
  9. 66
  10. 283
  11. 63
  12. 48
  13. 57
  14. 25
  15. 68
  16. 71
  17. 22
  18. 32
  19. 408
  20. 830
  21. 67
  22. 6
  23. 31
  24. 50
  25. 50
  26. 58
  27. 18
  28. 11
  29. 69
  30. 15
  31. 90
  32. 650
  33. 49
  34. 57
  35. 469
  36. 36
  37. 76
  38. 71
  39. 295
  40. 70

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