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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 629 · 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. 1.23 + 19 =
  2. 2.71 + 19 =
  3. 3.57 − 29 =
  4. 4.27 − 9 =
  5. 5.611 − 99 =
  6. 6.64 + 29 =
  7. 7.464 − 99 =
  8. 8.13 − 9 =
  9. 9.539 − 99 =
  10. 10.34 + 19 =
  11. 11.78 + 19 =
  12. 12.28 + 29 =
  13. 13.568 − 99 =
  14. 14.56 + 19 =
  15. 15.206 + 99 =
  16. 16.39 − 9 =
  17. 17.638 + 99 =
  18. 18.72 + 9 =
  19. 19.57 + 19 =
  20. 20.61 + 9 =
  21. 21.668 + 99 =
  22. 22.85 − 29 =
  23. 23.77 − 9 =
  24. 24.45 + 19 =
  25. 25.58 + 9 =
  26. 26.44 + 29 =
  27. 27.92 − 19 =
  28. 28.29 + 19 =
  29. 29.63 − 19 =
  30. 30.35 − 29 =
  31. 31.36 − 29 =
  32. 32.199 − 99 =
  33. 33.707 + 99 =
  34. 34.22 − 19 =
  35. 35.91 − 19 =
  36. 36.89 − 29 =
  37. 37.62 + 29 =
  38. 38.67 + 9 =
  39. 39.14 + 29 =
  40. 40.409 + 99 =

Answer key

  1. 42
  2. 90
  3. 28
  4. 18
  5. 512
  6. 93
  7. 365
  8. 4
  9. 440
  10. 53
  11. 97
  12. 57
  13. 469
  14. 75
  15. 305
  16. 30
  17. 737
  18. 81
  19. 76
  20. 70
  21. 767
  22. 56
  23. 68
  24. 64
  25. 67
  26. 73
  27. 73
  28. 48
  29. 44
  30. 6
  31. 7
  32. 100
  33. 806
  34. 3
  35. 72
  36. 60
  37. 91
  38. 76
  39. 43
  40. 508

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