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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 601 · 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. 1.469 + 99 =
  2. 2.86 − 9 =
  3. 3.431 − 99 =
  4. 4.653 + 99 =
  5. 5.358 − 99 =
  6. 6.108 − 29 =
  7. 7.51 − 9 =
  8. 8.42 − 9 =
  9. 9.34 + 19 =
  10. 10.72 − 19 =
  11. 11.27 − 9 =
  12. 12.50 − 19 =
  13. 13.228 + 99 =
  14. 14.628 + 99 =
  15. 15.50 + 19 =
  16. 16.763 + 99 =
  17. 17.49 − 9 =
  18. 18.61 − 29 =
  19. 19.80 + 29 =
  20. 20.61 − 9 =
  21. 21.78 + 9 =
  22. 22.73 + 19 =
  23. 23.43 − 9 =
  24. 24.58 + 19 =
  25. 25.62 − 9 =
  26. 26.92 − 29 =
  27. 27.61 − 19 =
  28. 28.16 + 29 =
  29. 29.174 + 99 =
  30. 30.23 − 9 =
  31. 31.48 + 19 =
  32. 32.68 − 9 =
  33. 33.523 − 99 =
  34. 34.78 − 19 =
  35. 35.18 + 9 =
  36. 36.39 − 29 =
  37. 37.349 + 99 =
  38. 38.72 + 19 =
  39. 39.649 − 99 =
  40. 40.48 − 9 =

Answer key

  1. 568
  2. 77
  3. 332
  4. 752
  5. 259
  6. 79
  7. 42
  8. 33
  9. 53
  10. 53
  11. 18
  12. 31
  13. 327
  14. 727
  15. 69
  16. 862
  17. 40
  18. 32
  19. 109
  20. 52
  21. 87
  22. 92
  23. 34
  24. 77
  25. 53
  26. 63
  27. 42
  28. 45
  29. 273
  30. 14
  31. 67
  32. 59
  33. 424
  34. 59
  35. 27
  36. 10
  37. 448
  38. 91
  39. 550
  40. 39

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