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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 226 · 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. 1.28 − 19 =
  2. 2.855 − 99 =
  3. 3.638 + 99 =
  4. 4.51 − 19 =
  5. 5.16 + 19 =
  6. 6.26 + 29 =
  7. 7.483 − 99 =
  8. 8.20 + 29 =
  9. 9.65 − 9 =
  10. 10.42 − 9 =
  11. 11.28 + 9 =
  12. 12.25 − 9 =
  13. 13.84 − 19 =
  14. 14.192 − 99 =
  15. 15.26 − 19 =
  16. 16.15 + 19 =
  17. 17.23 + 9 =
  18. 18.18 − 9 =
  19. 19.53 + 9 =
  20. 20.51 + 9 =
  21. 21.255 − 99 =
  22. 22.112 + 99 =
  23. 23.16 − 9 =
  24. 24.216 + 99 =
  25. 25.56 − 19 =
  26. 26.54 + 9 =
  27. 27.35 + 9 =
  28. 28.76 + 9 =
  29. 29.36 + 19 =
  30. 30.12 + 29 =
  31. 31.880 − 99 =
  32. 32.83 − 19 =
  33. 33.725 + 99 =
  34. 34.346 + 99 =
  35. 35.45 − 29 =
  36. 36.38 − 29 =
  37. 37.611 − 99 =
  38. 38.89 − 19 =
  39. 39.97 − 29 =
  40. 40.24 − 9 =

Answer key

  1. 9
  2. 756
  3. 737
  4. 32
  5. 35
  6. 55
  7. 384
  8. 49
  9. 56
  10. 33
  11. 37
  12. 16
  13. 65
  14. 93
  15. 7
  16. 34
  17. 32
  18. 9
  19. 62
  20. 60
  21. 156
  22. 211
  23. 7
  24. 315
  25. 37
  26. 63
  27. 44
  28. 85
  29. 55
  30. 41
  31. 781
  32. 64
  33. 824
  34. 445
  35. 16
  36. 9
  37. 512
  38. 70
  39. 68
  40. 15

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