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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 13 · 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. 1.669 − 99 =
  2. 2.34 + 9 =
  3. 3.37 − 29 =
  4. 4.105 − 29 =
  5. 5.31 + 29 =
  6. 6.50 − 29 =
  7. 7.23 + 19 =
  8. 8.61 − 29 =
  9. 9.38 + 9 =
  10. 10.85 − 29 =
  11. 11.33 − 9 =
  12. 12.538 + 99 =
  13. 13.361 − 99 =
  14. 14.798 − 99 =
  15. 15.33 + 19 =
  16. 16.73 + 19 =
  17. 17.675 + 99 =
  18. 18.358 − 99 =
  19. 19.42 − 9 =
  20. 20.71 + 29 =
  21. 21.271 − 99 =
  22. 22.35 − 9 =
  23. 23.80 + 19 =
  24. 24.70 + 9 =
  25. 25.187 − 99 =
  26. 26.247 + 99 =
  27. 27.77 + 9 =
  28. 28.652 + 99 =
  29. 29.512 − 99 =
  30. 30.38 + 19 =
  31. 31.39 − 19 =
  32. 32.75 − 19 =
  33. 33.895 − 99 =
  34. 34.27 + 19 =
  35. 35.55 − 29 =
  36. 36.413 − 99 =
  37. 37.25 − 9 =
  38. 38.80 + 29 =
  39. 39.281 + 99 =
  40. 40.426 − 99 =

Answer key

  1. 570
  2. 43
  3. 8
  4. 76
  5. 60
  6. 21
  7. 42
  8. 32
  9. 47
  10. 56
  11. 24
  12. 637
  13. 262
  14. 699
  15. 52
  16. 92
  17. 774
  18. 259
  19. 33
  20. 100
  21. 172
  22. 26
  23. 99
  24. 79
  25. 88
  26. 346
  27. 86
  28. 751
  29. 413
  30. 57
  31. 20
  32. 56
  33. 796
  34. 46
  35. 26
  36. 314
  37. 16
  38. 109
  39. 380
  40. 327

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