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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 851 · 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. 1.54 + 9 =
  2. 2.63 − 19 =
  3. 3.47 + 19 =
  4. 4.66 − 19 =
  5. 5.61 + 19 =
  6. 6.165 + 99 =
  7. 7.76 − 29 =
  8. 8.54 + 19 =
  9. 9.76 + 9 =
  10. 10.19 + 19 =
  11. 11.84 − 9 =
  12. 12.557 + 99 =
  13. 13.68 + 29 =
  14. 14.96 − 19 =
  15. 15.70 − 9 =
  16. 16.66 − 29 =
  17. 17.674 + 99 =
  18. 18.623 + 99 =
  19. 19.815 − 99 =
  20. 20.57 + 19 =
  21. 21.57 + 29 =
  22. 22.58 + 9 =
  23. 23.30 − 19 =
  24. 24.48 − 19 =
  25. 25.580 − 99 =
  26. 26.36 − 9 =
  27. 27.78 + 19 =
  28. 28.26 + 9 =
  29. 29.56 − 9 =
  30. 30.38 − 29 =
  31. 31.28 − 19 =
  32. 32.68 − 9 =
  33. 33.20 + 19 =
  34. 34.75 − 9 =
  35. 35.525 + 99 =
  36. 36.569 − 99 =
  37. 37.370 − 99 =
  38. 38.757 − 99 =
  39. 39.528 − 99 =
  40. 40.26 + 29 =

Answer key

  1. 63
  2. 44
  3. 66
  4. 47
  5. 80
  6. 264
  7. 47
  8. 73
  9. 85
  10. 38
  11. 75
  12. 656
  13. 97
  14. 77
  15. 61
  16. 37
  17. 773
  18. 722
  19. 716
  20. 76
  21. 86
  22. 67
  23. 11
  24. 29
  25. 481
  26. 27
  27. 97
  28. 35
  29. 47
  30. 9
  31. 9
  32. 59
  33. 39
  34. 66
  35. 624
  36. 470
  37. 271
  38. 658
  39. 429
  40. 55

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