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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 228 · 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. 1.44 + 19 =
  2. 2.24 + 19 =
  3. 3.491 − 99 =
  4. 4.32 + 19 =
  5. 5.54 + 9 =
  6. 6.51 + 19 =
  7. 7.31 + 9 =
  8. 8.268 + 99 =
  9. 9.622 + 99 =
  10. 10.713 + 99 =
  11. 11.468 + 99 =
  12. 12.397 + 99 =
  13. 13.48 + 9 =
  14. 14.80 + 9 =
  15. 15.58 + 19 =
  16. 16.87 − 9 =
  17. 17.29 + 9 =
  18. 18.222 − 99 =
  19. 19.56 + 29 =
  20. 20.65 − 9 =
  21. 21.46 + 29 =
  22. 22.19 + 19 =
  23. 23.59 + 9 =
  24. 24.85 − 9 =
  25. 25.49 + 29 =
  26. 26.74 − 9 =
  27. 27.46 − 29 =
  28. 28.54 + 29 =
  29. 29.41 − 19 =
  30. 30.65 + 19 =
  31. 31.378 + 99 =
  32. 32.102 − 29 =
  33. 33.30 + 9 =
  34. 34.75 + 29 =
  35. 35.75 − 9 =
  36. 36.44 + 29 =
  37. 37.28 + 29 =
  38. 38.120 + 99 =
  39. 39.19 + 9 =
  40. 40.83 − 29 =

Answer key

  1. 63
  2. 43
  3. 392
  4. 51
  5. 63
  6. 70
  7. 40
  8. 367
  9. 721
  10. 812
  11. 567
  12. 496
  13. 57
  14. 89
  15. 77
  16. 78
  17. 38
  18. 123
  19. 85
  20. 56
  21. 75
  22. 38
  23. 68
  24. 76
  25. 78
  26. 65
  27. 17
  28. 83
  29. 22
  30. 84
  31. 477
  32. 73
  33. 39
  34. 104
  35. 66
  36. 73
  37. 57
  38. 219
  39. 28
  40. 54

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