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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 506 · 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. 1.600 + 99 =
  2. 2.14 + 9 =
  3. 3.25 − 9 =
  4. 4.24 + 29 =
  5. 5.31 − 9 =
  6. 6.71 + 9 =
  7. 7.36 + 29 =
  8. 8.68 + 29 =
  9. 9.60 + 19 =
  10. 10.76 − 19 =
  11. 11.84 − 19 =
  12. 12.35 − 19 =
  13. 13.34 − 19 =
  14. 14.421 − 99 =
  15. 15.35 − 9 =
  16. 16.12 + 9 =
  17. 17.36 + 9 =
  18. 18.352 − 99 =
  19. 19.16 + 19 =
  20. 20.238 − 99 =
  21. 21.57 + 19 =
  22. 22.63 + 19 =
  23. 23.45 + 19 =
  24. 24.32 − 19 =
  25. 25.87 − 19 =
  26. 26.12 − 9 =
  27. 27.34 + 9 =
  28. 28.58 − 9 =
  29. 29.95 − 19 =
  30. 30.475 − 99 =
  31. 31.13 − 9 =
  32. 32.511 + 99 =
  33. 33.33 − 29 =
  34. 34.17 − 9 =
  35. 35.89 − 29 =
  36. 36.40 + 29 =
  37. 37.32 + 19 =
  38. 38.84 − 29 =
  39. 39.587 + 99 =
  40. 40.81 − 29 =

Answer key

  1. 699
  2. 23
  3. 16
  4. 53
  5. 22
  6. 80
  7. 65
  8. 97
  9. 79
  10. 57
  11. 65
  12. 16
  13. 15
  14. 322
  15. 26
  16. 21
  17. 45
  18. 253
  19. 35
  20. 139
  21. 76
  22. 82
  23. 64
  24. 13
  25. 68
  26. 3
  27. 43
  28. 49
  29. 76
  30. 376
  31. 4
  32. 610
  33. 4
  34. 8
  35. 60
  36. 69
  37. 51
  38. 55
  39. 686
  40. 52

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