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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 294 · 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. 1.84 − 29 =
  2. 2.39 + 29 =
  3. 3.244 − 99 =
  4. 4.30 − 19 =
  5. 5.370 − 99 =
  6. 6.44 + 19 =
  7. 7.46 − 9 =
  8. 8.690 − 99 =
  9. 9.32 − 9 =
  10. 10.71 − 9 =
  11. 11.216 + 99 =
  12. 12.55 + 19 =
  13. 13.361 − 99 =
  14. 14.765 − 99 =
  15. 15.26 + 29 =
  16. 16.74 − 19 =
  17. 17.64 + 19 =
  18. 18.48 + 9 =
  19. 19.45 − 9 =
  20. 20.53 − 29 =
  21. 21.80 + 19 =
  22. 22.137 + 99 =
  23. 23.20 + 19 =
  24. 24.62 + 9 =
  25. 25.891 − 99 =
  26. 26.418 − 99 =
  27. 27.78 − 19 =
  28. 28.46 − 19 =
  29. 29.95 − 19 =
  30. 30.49 + 29 =
  31. 31.87 − 19 =
  32. 32.261 + 99 =
  33. 33.14 + 19 =
  34. 34.26 + 9 =
  35. 35.500 − 99 =
  36. 36.40 − 9 =
  37. 37.23 − 19 =
  38. 38.676 + 99 =
  39. 39.82 − 29 =
  40. 40.33 − 19 =

Answer key

  1. 55
  2. 68
  3. 145
  4. 11
  5. 271
  6. 63
  7. 37
  8. 591
  9. 23
  10. 62
  11. 315
  12. 74
  13. 262
  14. 666
  15. 55
  16. 55
  17. 83
  18. 57
  19. 36
  20. 24
  21. 99
  22. 236
  23. 39
  24. 71
  25. 792
  26. 319
  27. 59
  28. 27
  29. 76
  30. 78
  31. 68
  32. 360
  33. 33
  34. 35
  35. 401
  36. 31
  37. 4
  38. 775
  39. 53
  40. 14

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