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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 413 · 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. 1.30 + 29 =
  2. 2.19 − 9 =
  3. 3.66 + 19 =
  4. 4.86 − 9 =
  5. 5.27 + 9 =
  6. 6.831 − 99 =
  7. 7.381 + 99 =
  8. 8.685 − 99 =
  9. 9.61 − 29 =
  10. 10.62 + 19 =
  11. 11.446 − 99 =
  12. 12.34 − 29 =
  13. 13.93 − 29 =
  14. 14.45 − 29 =
  15. 15.51 + 9 =
  16. 16.135 + 99 =
  17. 17.56 − 9 =
  18. 18.34 − 9 =
  19. 19.35 − 9 =
  20. 20.723 + 99 =
  21. 21.23 − 9 =
  22. 22.192 − 99 =
  23. 23.71 − 29 =
  24. 24.27 + 29 =
  25. 25.558 + 99 =
  26. 26.79 + 29 =
  27. 27.38 − 19 =
  28. 28.41 − 29 =
  29. 29.75 − 9 =
  30. 30.38 + 9 =
  31. 31.77 + 9 =
  32. 32.74 − 29 =
  33. 33.87 − 19 =
  34. 34.97 − 29 =
  35. 35.421 + 99 =
  36. 36.827 − 99 =
  37. 37.96 − 29 =
  38. 38.68 + 29 =
  39. 39.74 + 19 =
  40. 40.30 − 19 =

Answer key

  1. 59
  2. 10
  3. 85
  4. 77
  5. 36
  6. 732
  7. 480
  8. 586
  9. 32
  10. 81
  11. 347
  12. 5
  13. 64
  14. 16
  15. 60
  16. 234
  17. 47
  18. 25
  19. 26
  20. 822
  21. 14
  22. 93
  23. 42
  24. 56
  25. 657
  26. 108
  27. 19
  28. 12
  29. 66
  30. 47
  31. 86
  32. 45
  33. 68
  34. 68
  35. 520
  36. 728
  37. 67
  38. 97
  39. 93
  40. 11

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