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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 81 · 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. 1.73 + 29 =
  2. 2.55 − 29 =
  3. 3.30 + 29 =
  4. 4.37 + 19 =
  5. 5.38 − 29 =
  6. 6.40 − 9 =
  7. 7.29 + 9 =
  8. 8.45 − 19 =
  9. 9.67 − 9 =
  10. 10.49 + 9 =
  11. 11.12 + 29 =
  12. 12.22 + 9 =
  13. 13.80 + 9 =
  14. 14.99 − 19 =
  15. 15.79 − 9 =
  16. 16.550 + 99 =
  17. 17.72 + 9 =
  18. 18.54 + 9 =
  19. 19.35 − 29 =
  20. 20.50 + 29 =
  21. 21.353 − 99 =
  22. 22.57 − 19 =
  23. 23.644 + 99 =
  24. 24.74 − 29 =
  25. 25.22 + 29 =
  26. 26.726 − 99 =
  27. 27.59 − 9 =
  28. 28.28 + 9 =
  29. 29.408 − 99 =
  30. 30.458 − 99 =
  31. 31.82 − 9 =
  32. 32.79 − 19 =
  33. 33.314 + 99 =
  34. 34.48 + 9 =
  35. 35.48 − 9 =
  36. 36.43 − 29 =
  37. 37.73 − 19 =
  38. 38.75 + 9 =
  39. 39.39 + 19 =
  40. 40.834 − 99 =

Answer key

  1. 102
  2. 26
  3. 59
  4. 56
  5. 9
  6. 31
  7. 38
  8. 26
  9. 58
  10. 58
  11. 41
  12. 31
  13. 89
  14. 80
  15. 70
  16. 649
  17. 81
  18. 63
  19. 6
  20. 79
  21. 254
  22. 38
  23. 743
  24. 45
  25. 51
  26. 627
  27. 50
  28. 37
  29. 309
  30. 359
  31. 73
  32. 60
  33. 413
  34. 57
  35. 39
  36. 14
  37. 54
  38. 84
  39. 58
  40. 735

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