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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 237 · 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. 1.44 − 19 =
  2. 2.73 − 19 =
  3. 3.339 − 99 =
  4. 4.44 − 9 =
  5. 5.315 − 99 =
  6. 6.780 + 99 =
  7. 7.334 − 99 =
  8. 8.43 + 19 =
  9. 9.19 − 9 =
  10. 10.665 − 99 =
  11. 11.750 − 99 =
  12. 12.614 − 99 =
  13. 13.105 + 99 =
  14. 14.63 + 9 =
  15. 15.898 − 99 =
  16. 16.49 + 19 =
  17. 17.829 − 99 =
  18. 18.49 + 9 =
  19. 19.67 + 19 =
  20. 20.76 + 19 =
  21. 21.64 − 9 =
  22. 22.55 + 9 =
  23. 23.21 + 29 =
  24. 24.35 + 19 =
  25. 25.80 + 29 =
  26. 26.34 + 9 =
  27. 27.70 − 9 =
  28. 28.32 − 9 =
  29. 29.859 − 99 =
  30. 30.78 + 19 =
  31. 31.12 + 19 =
  32. 32.588 + 99 =
  33. 33.38 + 19 =
  34. 34.58 + 29 =
  35. 35.66 + 9 =
  36. 36.268 − 99 =
  37. 37.99 − 29 =
  38. 38.73 + 29 =
  39. 39.251 + 99 =
  40. 40.66 − 29 =

Answer key

  1. 25
  2. 54
  3. 240
  4. 35
  5. 216
  6. 879
  7. 235
  8. 62
  9. 10
  10. 566
  11. 651
  12. 515
  13. 204
  14. 72
  15. 799
  16. 68
  17. 730
  18. 58
  19. 86
  20. 95
  21. 55
  22. 64
  23. 50
  24. 54
  25. 109
  26. 43
  27. 61
  28. 23
  29. 760
  30. 97
  31. 31
  32. 687
  33. 57
  34. 87
  35. 75
  36. 169
  37. 70
  38. 102
  39. 350
  40. 37

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