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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 493 · 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. 1.108 + 99 =
  2. 2.30 + 29 =
  3. 3.67 − 29 =
  4. 4.106 − 29 =
  5. 5.654 − 99 =
  6. 6.85 − 29 =
  7. 7.40 − 19 =
  8. 8.68 − 9 =
  9. 9.493 − 99 =
  10. 10.32 − 19 =
  11. 11.87 − 19 =
  12. 12.16 + 9 =
  13. 13.317 − 99 =
  14. 14.65 − 9 =
  15. 15.24 + 19 =
  16. 16.414 + 99 =
  17. 17.14 + 9 =
  18. 18.14 + 19 =
  19. 19.58 − 19 =
  20. 20.42 − 19 =
  21. 21.29 + 9 =
  22. 22.14 + 29 =
  23. 23.40 + 9 =
  24. 24.22 + 19 =
  25. 25.55 − 9 =
  26. 26.545 + 99 =
  27. 27.88 − 9 =
  28. 28.39 − 19 =
  29. 29.64 − 29 =
  30. 30.81 − 29 =
  31. 31.289 + 99 =
  32. 32.153 + 99 =
  33. 33.87 − 9 =
  34. 34.563 − 99 =
  35. 35.48 − 29 =
  36. 36.47 + 29 =
  37. 37.65 − 19 =
  38. 38.20 + 19 =
  39. 39.72 + 9 =
  40. 40.76 − 9 =

Answer key

  1. 207
  2. 59
  3. 38
  4. 77
  5. 555
  6. 56
  7. 21
  8. 59
  9. 394
  10. 13
  11. 68
  12. 25
  13. 218
  14. 56
  15. 43
  16. 513
  17. 23
  18. 33
  19. 39
  20. 23
  21. 38
  22. 43
  23. 49
  24. 41
  25. 46
  26. 644
  27. 79
  28. 20
  29. 35
  30. 52
  31. 388
  32. 252
  33. 78
  34. 464
  35. 19
  36. 76
  37. 46
  38. 39
  39. 81
  40. 67

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