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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 579 · 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. 1.14 + 19 =
  2. 2.34 − 29 =
  3. 3.66 − 29 =
  4. 4.14 + 29 =
  5. 5.74 + 29 =
  6. 6.47 + 19 =
  7. 7.293 + 99 =
  8. 8.442 − 99 =
  9. 9.34 + 9 =
  10. 10.502 + 99 =
  11. 11.87 − 19 =
  12. 12.86 − 9 =
  13. 13.32 + 9 =
  14. 14.50 + 29 =
  15. 15.63 + 9 =
  16. 16.21 + 9 =
  17. 17.762 + 99 =
  18. 18.72 + 19 =
  19. 19.23 + 29 =
  20. 20.38 − 9 =
  21. 21.29 + 29 =
  22. 22.42 − 19 =
  23. 23.53 − 9 =
  24. 24.46 + 9 =
  25. 25.29 − 19 =
  26. 26.38 + 29 =
  27. 27.228 + 99 =
  28. 28.21 + 19 =
  29. 29.87 − 9 =
  30. 30.40 + 9 =
  31. 31.75 − 29 =
  32. 32.95 − 19 =
  33. 33.536 − 99 =
  34. 34.349 + 99 =
  35. 35.44 + 19 =
  36. 36.54 + 19 =
  37. 37.86 − 29 =
  38. 38.13 + 9 =
  39. 39.743 + 99 =
  40. 40.257 + 99 =

Answer key

  1. 33
  2. 5
  3. 37
  4. 43
  5. 103
  6. 66
  7. 392
  8. 343
  9. 43
  10. 601
  11. 68
  12. 77
  13. 41
  14. 79
  15. 72
  16. 30
  17. 861
  18. 91
  19. 52
  20. 29
  21. 58
  22. 23
  23. 44
  24. 55
  25. 10
  26. 67
  27. 327
  28. 40
  29. 78
  30. 49
  31. 46
  32. 76
  33. 437
  34. 448
  35. 63
  36. 73
  37. 57
  38. 22
  39. 842
  40. 356

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