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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 419 · 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. 2.96 − 29 =
  3. 3.49 − 19 =
  4. 4.24 + 9 =
  5. 5.212 − 99 =
  6. 6.61 − 9 =
  7. 7.65 − 19 =
  8. 8.48 + 9 =
  9. 9.80 + 9 =
  10. 10.312 + 99 =
  11. 11.47 − 9 =
  12. 12.14 − 9 =
  13. 13.70 − 29 =
  14. 14.23 + 29 =
  15. 15.24 − 9 =
  16. 16.227 − 99 =
  17. 17.17 − 9 =
  18. 18.117 + 99 =
  19. 19.43 + 19 =
  20. 20.119 + 99 =
  21. 21.58 − 29 =
  22. 22.94 − 19 =
  23. 23.59 + 9 =
  24. 24.22 + 9 =
  25. 25.457 − 99 =
  26. 26.605 + 99 =
  27. 27.47 + 19 =
  28. 28.816 − 99 =
  29. 29.63 − 29 =
  30. 30.46 + 19 =
  31. 31.45 + 19 =
  32. 32.35 + 9 =
  33. 33.566 + 99 =
  34. 34.52 + 9 =
  35. 35.33 − 9 =
  36. 36.38 − 9 =
  37. 37.160 − 99 =
  38. 38.62 + 9 =
  39. 39.57 + 9 =
  40. 40.98 − 29 =

Answer key

  1. 12
  2. 67
  3. 30
  4. 33
  5. 113
  6. 52
  7. 46
  8. 57
  9. 89
  10. 411
  11. 38
  12. 5
  13. 41
  14. 52
  15. 15
  16. 128
  17. 8
  18. 216
  19. 62
  20. 218
  21. 29
  22. 75
  23. 68
  24. 31
  25. 358
  26. 704
  27. 66
  28. 717
  29. 34
  30. 65
  31. 64
  32. 44
  33. 665
  34. 61
  35. 24
  36. 29
  37. 61
  38. 71
  39. 66
  40. 69

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