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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 89 · 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. 1.39 − 29 =
  2. 2.98 − 29 =
  3. 3.27 + 19 =
  4. 4.51 + 9 =
  5. 5.580 + 99 =
  6. 6.50 + 19 =
  7. 7.30 + 9 =
  8. 8.453 + 99 =
  9. 9.470 − 99 =
  10. 10.21 + 29 =
  11. 11.16 + 9 =
  12. 12.31 + 19 =
  13. 13.506 + 99 =
  14. 14.44 + 29 =
  15. 15.17 + 19 =
  16. 16.499 + 99 =
  17. 17.174 − 99 =
  18. 18.36 + 29 =
  19. 19.31 − 19 =
  20. 20.75 + 19 =
  21. 21.656 − 99 =
  22. 22.85 − 9 =
  23. 23.798 − 99 =
  24. 24.54 − 9 =
  25. 25.27 − 9 =
  26. 26.21 + 9 =
  27. 27.37 − 19 =
  28. 28.808 − 99 =
  29. 29.627 + 99 =
  30. 30.67 − 29 =
  31. 31.12 − 9 =
  32. 32.53 − 9 =
  33. 33.63 + 29 =
  34. 34.40 + 19 =
  35. 35.85 − 29 =
  36. 36.65 + 9 =
  37. 37.34 − 19 =
  38. 38.167 + 99 =
  39. 39.335 − 99 =
  40. 40.652 − 99 =

Answer key

  1. 10
  2. 69
  3. 46
  4. 60
  5. 679
  6. 69
  7. 39
  8. 552
  9. 371
  10. 50
  11. 25
  12. 50
  13. 605
  14. 73
  15. 36
  16. 598
  17. 75
  18. 65
  19. 12
  20. 94
  21. 557
  22. 76
  23. 699
  24. 45
  25. 18
  26. 30
  27. 18
  28. 709
  29. 726
  30. 38
  31. 3
  32. 44
  33. 92
  34. 59
  35. 56
  36. 74
  37. 15
  38. 266
  39. 236
  40. 553

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