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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 758 · 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. 1.97 − 19 =
  2. 2.95 − 19 =
  3. 3.59 − 9 =
  4. 4.38 + 9 =
  5. 5.60 − 9 =
  6. 6.43 + 29 =
  7. 7.54 + 29 =
  8. 8.56 − 9 =
  9. 9.41 + 9 =
  10. 10.386 + 99 =
  11. 11.30 + 19 =
  12. 12.837 − 99 =
  13. 13.195 − 99 =
  14. 14.557 − 99 =
  15. 15.23 + 29 =
  16. 16.85 − 9 =
  17. 17.30 + 9 =
  18. 18.54 − 9 =
  19. 19.497 − 99 =
  20. 20.526 − 99 =
  21. 21.61 + 9 =
  22. 22.63 − 29 =
  23. 23.184 + 99 =
  24. 24.63 − 9 =
  25. 25.12 + 29 =
  26. 26.203 + 99 =
  27. 27.13 + 9 =
  28. 28.75 + 9 =
  29. 29.16 + 9 =
  30. 30.28 + 29 =
  31. 31.31 + 29 =
  32. 32.538 − 99 =
  33. 33.66 − 9 =
  34. 34.71 + 9 =
  35. 35.75 − 9 =
  36. 36.75 + 29 =
  37. 37.161 + 99 =
  38. 38.50 + 9 =
  39. 39.29 + 9 =
  40. 40.74 − 9 =

Answer key

  1. 78
  2. 76
  3. 50
  4. 47
  5. 51
  6. 72
  7. 83
  8. 47
  9. 50
  10. 485
  11. 49
  12. 738
  13. 96
  14. 458
  15. 52
  16. 76
  17. 39
  18. 45
  19. 398
  20. 427
  21. 70
  22. 34
  23. 283
  24. 54
  25. 41
  26. 302
  27. 22
  28. 84
  29. 25
  30. 57
  31. 60
  32. 439
  33. 57
  34. 80
  35. 66
  36. 104
  37. 260
  38. 59
  39. 38
  40. 65

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