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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 746 · 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. 1.90 − 29 =
  2. 2.46 + 29 =
  3. 3.20 + 9 =
  4. 4.46 − 29 =
  5. 5.899 − 99 =
  6. 6.32 − 29 =
  7. 7.102 − 29 =
  8. 8.74 − 29 =
  9. 9.51 + 19 =
  10. 10.68 + 29 =
  11. 11.788 + 99 =
  12. 12.99 − 29 =
  13. 13.727 + 99 =
  14. 14.55 − 29 =
  15. 15.69 + 29 =
  16. 16.774 − 99 =
  17. 17.105 − 29 =
  18. 18.54 − 19 =
  19. 19.14 + 9 =
  20. 20.71 − 29 =
  21. 21.46 − 9 =
  22. 22.57 − 19 =
  23. 23.56 + 29 =
  24. 24.62 + 29 =
  25. 25.317 + 99 =
  26. 26.79 − 29 =
  27. 27.58 + 19 =
  28. 28.49 + 19 =
  29. 29.40 + 9 =
  30. 30.27 − 9 =
  31. 31.76 − 9 =
  32. 32.29 + 9 =
  33. 33.80 − 9 =
  34. 34.473 − 99 =
  35. 35.251 − 99 =
  36. 36.72 − 19 =
  37. 37.104 − 29 =
  38. 38.68 − 19 =
  39. 39.566 + 99 =
  40. 40.39 − 29 =

Answer key

  1. 61
  2. 75
  3. 29
  4. 17
  5. 800
  6. 3
  7. 73
  8. 45
  9. 70
  10. 97
  11. 887
  12. 70
  13. 826
  14. 26
  15. 98
  16. 675
  17. 76
  18. 35
  19. 23
  20. 42
  21. 37
  22. 38
  23. 85
  24. 91
  25. 416
  26. 50
  27. 77
  28. 68
  29. 49
  30. 18
  31. 67
  32. 38
  33. 71
  34. 374
  35. 152
  36. 53
  37. 75
  38. 49
  39. 665
  40. 10

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