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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 50 · 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. 1.190 − 99 =
  2. 2.298 − 99 =
  3. 3.71 − 19 =
  4. 4.49 + 29 =
  5. 5.53 − 9 =
  6. 6.667 + 99 =
  7. 7.45 + 29 =
  8. 8.70 + 29 =
  9. 9.30 + 9 =
  10. 10.323 + 99 =
  11. 11.25 + 19 =
  12. 12.42 − 9 =
  13. 13.73 − 29 =
  14. 14.33 + 19 =
  15. 15.350 − 99 =
  16. 16.69 + 29 =
  17. 17.16 + 29 =
  18. 18.13 + 29 =
  19. 19.56 + 19 =
  20. 20.13 + 9 =
  21. 21.46 − 9 =
  22. 22.25 − 19 =
  23. 23.57 + 9 =
  24. 24.182 − 99 =
  25. 25.56 − 9 =
  26. 26.34 + 29 =
  27. 27.20 − 9 =
  28. 28.32 − 19 =
  29. 29.22 − 19 =
  30. 30.325 − 99 =
  31. 31.455 + 99 =
  32. 32.96 − 29 =
  33. 33.32 + 9 =
  34. 34.87 − 29 =
  35. 35.394 + 99 =
  36. 36.38 − 29 =
  37. 37.21 − 9 =
  38. 38.99 − 19 =
  39. 39.55 + 19 =
  40. 40.216 − 99 =

Answer key

  1. 91
  2. 199
  3. 52
  4. 78
  5. 44
  6. 766
  7. 74
  8. 99
  9. 39
  10. 422
  11. 44
  12. 33
  13. 44
  14. 52
  15. 251
  16. 98
  17. 45
  18. 42
  19. 75
  20. 22
  21. 37
  22. 6
  23. 66
  24. 83
  25. 47
  26. 63
  27. 11
  28. 13
  29. 3
  30. 226
  31. 554
  32. 67
  33. 41
  34. 58
  35. 493
  36. 9
  37. 12
  38. 80
  39. 74
  40. 117

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