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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 539 · 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. 1.105 − 29 =
  2. 2.72 − 29 =
  3. 3.80 + 29 =
  4. 4.39 − 9 =
  5. 5.43 − 19 =
  6. 6.48 − 9 =
  7. 7.61 + 9 =
  8. 8.656 + 99 =
  9. 9.74 + 29 =
  10. 10.73 − 29 =
  11. 11.756 − 99 =
  12. 12.35 + 9 =
  13. 13.65 − 19 =
  14. 14.38 + 9 =
  15. 15.746 + 99 =
  16. 16.46 − 19 =
  17. 17.425 − 99 =
  18. 18.23 − 9 =
  19. 19.33 − 29 =
  20. 20.18 + 19 =
  21. 21.80 − 9 =
  22. 22.77 + 19 =
  23. 23.52 − 19 =
  24. 24.78 + 9 =
  25. 25.66 + 9 =
  26. 26.43 + 9 =
  27. 27.62 − 19 =
  28. 28.613 + 99 =
  29. 29.68 + 19 =
  30. 30.173 − 99 =
  31. 31.38 + 19 =
  32. 32.35 + 29 =
  33. 33.90 − 29 =
  34. 34.60 − 9 =
  35. 35.28 + 9 =
  36. 36.107 − 29 =
  37. 37.77 − 9 =
  38. 38.95 − 29 =
  39. 39.22 − 9 =
  40. 40.26 − 19 =

Answer key

  1. 76
  2. 43
  3. 109
  4. 30
  5. 24
  6. 39
  7. 70
  8. 755
  9. 103
  10. 44
  11. 657
  12. 44
  13. 46
  14. 47
  15. 845
  16. 27
  17. 326
  18. 14
  19. 4
  20. 37
  21. 71
  22. 96
  23. 33
  24. 87
  25. 75
  26. 52
  27. 43
  28. 712
  29. 87
  30. 74
  31. 57
  32. 64
  33. 61
  34. 51
  35. 37
  36. 78
  37. 68
  38. 66
  39. 13
  40. 7

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