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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 117 · 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. 1.50 − 9 =
  2. 2.46 + 19 =
  3. 3.42 + 9 =
  4. 4.62 − 9 =
  5. 5.440 + 99 =
  6. 6.78 − 29 =
  7. 7.48 + 29 =
  8. 8.47 + 29 =
  9. 9.66 − 9 =
  10. 10.184 + 99 =
  11. 11.42 + 19 =
  12. 12.34 − 19 =
  13. 13.40 − 19 =
  14. 14.34 − 9 =
  15. 15.514 + 99 =
  16. 16.29 − 9 =
  17. 17.53 + 9 =
  18. 18.47 − 9 =
  19. 19.70 + 29 =
  20. 20.62 + 29 =
  21. 21.45 − 29 =
  22. 22.40 + 29 =
  23. 23.16 + 29 =
  24. 24.14 + 9 =
  25. 25.106 − 29 =
  26. 26.470 − 99 =
  27. 27.483 − 99 =
  28. 28.429 + 99 =
  29. 29.817 − 99 =
  30. 30.58 − 19 =
  31. 31.24 − 19 =
  32. 32.16 + 19 =
  33. 33.67 − 29 =
  34. 34.44 + 29 =
  35. 35.51 + 29 =
  36. 36.104 − 29 =
  37. 37.61 − 9 =
  38. 38.28 + 9 =
  39. 39.57 − 29 =
  40. 40.55 − 19 =

Answer key

  1. 41
  2. 65
  3. 51
  4. 53
  5. 539
  6. 49
  7. 77
  8. 76
  9. 57
  10. 283
  11. 61
  12. 15
  13. 21
  14. 25
  15. 613
  16. 20
  17. 62
  18. 38
  19. 99
  20. 91
  21. 16
  22. 69
  23. 45
  24. 23
  25. 77
  26. 371
  27. 384
  28. 528
  29. 718
  30. 39
  31. 5
  32. 35
  33. 38
  34. 73
  35. 80
  36. 75
  37. 52
  38. 37
  39. 28
  40. 36

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