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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 274 · 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. 1.56 + 29 =
  2. 2.42 + 9 =
  3. 3.609 − 99 =
  4. 4.69 + 29 =
  5. 5.51 − 29 =
  6. 6.53 + 9 =
  7. 7.30 − 9 =
  8. 8.42 − 29 =
  9. 9.596 + 99 =
  10. 10.68 + 19 =
  11. 11.75 + 19 =
  12. 12.76 − 9 =
  13. 13.230 − 99 =
  14. 14.443 + 99 =
  15. 15.23 − 9 =
  16. 16.22 + 9 =
  17. 17.160 + 99 =
  18. 18.40 + 19 =
  19. 19.26 − 19 =
  20. 20.72 − 19 =
  21. 21.561 + 99 =
  22. 22.58 + 19 =
  23. 23.715 + 99 =
  24. 24.36 + 29 =
  25. 25.51 + 19 =
  26. 26.46 − 29 =
  27. 27.295 + 99 =
  28. 28.50 − 29 =
  29. 29.68 − 29 =
  30. 30.32 + 19 =
  31. 31.892 − 99 =
  32. 32.600 + 99 =
  33. 33.302 + 99 =
  34. 34.39 + 29 =
  35. 35.64 + 29 =
  36. 36.81 − 9 =
  37. 37.14 + 9 =
  38. 38.109 − 29 =
  39. 39.437 + 99 =
  40. 40.145 + 99 =

Answer key

  1. 85
  2. 51
  3. 510
  4. 98
  5. 22
  6. 62
  7. 21
  8. 13
  9. 695
  10. 87
  11. 94
  12. 67
  13. 131
  14. 542
  15. 14
  16. 31
  17. 259
  18. 59
  19. 7
  20. 53
  21. 660
  22. 77
  23. 814
  24. 65
  25. 70
  26. 17
  27. 394
  28. 21
  29. 39
  30. 51
  31. 793
  32. 699
  33. 401
  34. 68
  35. 93
  36. 72
  37. 23
  38. 80
  39. 536
  40. 244

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