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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 668 · 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. 1.72 − 9 =
  2. 2.33 − 29 =
  3. 3.77 − 29 =
  4. 4.30 + 29 =
  5. 5.37 − 19 =
  6. 6.38 − 9 =
  7. 7.82 − 19 =
  8. 8.834 − 99 =
  9. 9.44 − 19 =
  10. 10.79 + 29 =
  11. 11.67 − 19 =
  12. 12.559 − 99 =
  13. 13.79 − 19 =
  14. 14.25 + 19 =
  15. 15.42 − 19 =
  16. 16.87 − 29 =
  17. 17.51 − 9 =
  18. 18.79 − 9 =
  19. 19.52 − 29 =
  20. 20.287 − 99 =
  21. 21.33 + 29 =
  22. 22.28 + 29 =
  23. 23.74 − 9 =
  24. 24.137 + 99 =
  25. 25.288 − 99 =
  26. 26.771 + 99 =
  27. 27.356 − 99 =
  28. 28.15 − 9 =
  29. 29.93 − 29 =
  30. 30.71 + 19 =
  31. 31.25 + 9 =
  32. 32.103 − 29 =
  33. 33.71 + 9 =
  34. 34.113 + 99 =
  35. 35.76 + 9 =
  36. 36.459 + 99 =
  37. 37.28 + 9 =
  38. 38.51 + 9 =
  39. 39.704 + 99 =
  40. 40.61 + 29 =

Answer key

  1. 63
  2. 4
  3. 48
  4. 59
  5. 18
  6. 29
  7. 63
  8. 735
  9. 25
  10. 108
  11. 48
  12. 460
  13. 60
  14. 44
  15. 23
  16. 58
  17. 42
  18. 70
  19. 23
  20. 188
  21. 62
  22. 57
  23. 65
  24. 236
  25. 189
  26. 870
  27. 257
  28. 6
  29. 64
  30. 90
  31. 34
  32. 74
  33. 80
  34. 212
  35. 85
  36. 558
  37. 37
  38. 60
  39. 803
  40. 90

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