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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 719 · 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. 1.79 + 29 =
  2. 2.673 + 99 =
  3. 3.59 − 19 =
  4. 4.54 − 19 =
  5. 5.75 + 9 =
  6. 6.417 − 99 =
  7. 7.56 − 9 =
  8. 8.61 + 29 =
  9. 9.251 − 99 =
  10. 10.285 + 99 =
  11. 11.25 + 19 =
  12. 12.18 + 9 =
  13. 13.48 − 29 =
  14. 14.14 + 29 =
  15. 15.442 − 99 =
  16. 16.200 + 99 =
  17. 17.50 + 19 =
  18. 18.12 + 9 =
  19. 19.59 + 9 =
  20. 20.27 − 9 =
  21. 21.744 + 99 =
  22. 22.52 + 19 =
  23. 23.52 − 29 =
  24. 24.180 − 99 =
  25. 25.451 − 99 =
  26. 26.30 + 19 =
  27. 27.79 − 9 =
  28. 28.19 − 9 =
  29. 29.85 − 19 =
  30. 30.95 − 29 =
  31. 31.45 − 9 =
  32. 32.68 + 19 =
  33. 33.27 + 9 =
  34. 34.555 + 99 =
  35. 35.78 + 9 =
  36. 36.60 + 19 =
  37. 37.60 − 19 =
  38. 38.46 + 29 =
  39. 39.384 − 99 =
  40. 40.44 + 9 =

Answer key

  1. 108
  2. 772
  3. 40
  4. 35
  5. 84
  6. 318
  7. 47
  8. 90
  9. 152
  10. 384
  11. 44
  12. 27
  13. 19
  14. 43
  15. 343
  16. 299
  17. 69
  18. 21
  19. 68
  20. 18
  21. 843
  22. 71
  23. 23
  24. 81
  25. 352
  26. 49
  27. 70
  28. 10
  29. 66
  30. 66
  31. 36
  32. 87
  33. 36
  34. 654
  35. 87
  36. 79
  37. 41
  38. 75
  39. 285
  40. 53

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