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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 954 · 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. 1.41 − 29 =
  2. 2.84 − 29 =
  3. 3.77 − 29 =
  4. 4.24 − 19 =
  5. 5.652 + 99 =
  6. 6.24 + 9 =
  7. 7.64 + 29 =
  8. 8.46 − 9 =
  9. 9.714 + 99 =
  10. 10.337 + 99 =
  11. 11.65 − 19 =
  12. 12.329 + 99 =
  13. 13.835 − 99 =
  14. 14.77 + 19 =
  15. 15.32 + 9 =
  16. 16.92 − 19 =
  17. 17.73 + 19 =
  18. 18.65 + 29 =
  19. 19.97 − 19 =
  20. 20.101 − 29 =
  21. 21.58 + 19 =
  22. 22.302 + 99 =
  23. 23.88 − 9 =
  24. 24.44 − 29 =
  25. 25.895 − 99 =
  26. 26.35 + 29 =
  27. 27.593 + 99 =
  28. 28.418 − 99 =
  29. 29.47 + 9 =
  30. 30.217 − 99 =
  31. 31.132 + 99 =
  32. 32.75 + 9 =
  33. 33.300 − 99 =
  34. 34.600 + 99 =
  35. 35.48 + 9 =
  36. 36.99 − 29 =
  37. 37.20 − 9 =
  38. 38.94 − 29 =
  39. 39.83 − 19 =
  40. 40.59 + 29 =

Answer key

  1. 12
  2. 55
  3. 48
  4. 5
  5. 751
  6. 33
  7. 93
  8. 37
  9. 813
  10. 436
  11. 46
  12. 428
  13. 736
  14. 96
  15. 41
  16. 73
  17. 92
  18. 94
  19. 78
  20. 72
  21. 77
  22. 401
  23. 79
  24. 15
  25. 796
  26. 64
  27. 692
  28. 319
  29. 56
  30. 118
  31. 231
  32. 84
  33. 201
  34. 699
  35. 57
  36. 70
  37. 11
  38. 65
  39. 64
  40. 88

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