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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 134 · 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. 1.49 − 19 =
  2. 2.81 − 19 =
  3. 3.73 − 9 =
  4. 4.109 − 29 =
  5. 5.21 + 9 =
  6. 6.14 + 9 =
  7. 7.335 + 99 =
  8. 8.17 − 9 =
  9. 9.56 − 9 =
  10. 10.658 − 99 =
  11. 11.47 − 29 =
  12. 12.568 − 99 =
  13. 13.563 + 99 =
  14. 14.15 + 19 =
  15. 15.28 + 9 =
  16. 16.80 + 19 =
  17. 17.72 − 9 =
  18. 18.738 + 99 =
  19. 19.211 + 99 =
  20. 20.80 − 29 =
  21. 21.740 − 99 =
  22. 22.755 + 99 =
  23. 23.62 + 29 =
  24. 24.619 − 99 =
  25. 25.98 − 19 =
  26. 26.61 − 9 =
  27. 27.53 + 19 =
  28. 28.411 − 99 =
  29. 29.38 − 9 =
  30. 30.89 − 19 =
  31. 31.20 + 9 =
  32. 32.70 + 19 =
  33. 33.858 − 99 =
  34. 34.726 − 99 =
  35. 35.35 − 29 =
  36. 36.42 + 9 =
  37. 37.46 + 9 =
  38. 38.256 + 99 =
  39. 39.12 + 9 =
  40. 40.72 + 29 =

Answer key

  1. 30
  2. 62
  3. 64
  4. 80
  5. 30
  6. 23
  7. 434
  8. 8
  9. 47
  10. 559
  11. 18
  12. 469
  13. 662
  14. 34
  15. 37
  16. 99
  17. 63
  18. 837
  19. 310
  20. 51
  21. 641
  22. 854
  23. 91
  24. 520
  25. 79
  26. 52
  27. 72
  28. 312
  29. 29
  30. 70
  31. 29
  32. 89
  33. 759
  34. 627
  35. 6
  36. 51
  37. 55
  38. 355
  39. 21
  40. 101

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