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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 438 · 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. 1.55 − 19 =
  2. 2.72 + 19 =
  3. 3.31 + 9 =
  4. 4.50 − 9 =
  5. 5.15 + 29 =
  6. 6.76 − 19 =
  7. 7.75 − 29 =
  8. 8.441 − 99 =
  9. 9.26 − 9 =
  10. 10.520 + 99 =
  11. 11.67 − 9 =
  12. 12.104 − 29 =
  13. 13.61 + 29 =
  14. 14.45 − 29 =
  15. 15.24 + 19 =
  16. 16.96 − 19 =
  17. 17.74 + 9 =
  18. 18.102 − 29 =
  19. 19.197 + 99 =
  20. 20.56 − 19 =
  21. 21.39 + 9 =
  22. 22.58 + 9 =
  23. 23.81 − 29 =
  24. 24.13 + 29 =
  25. 25.42 − 9 =
  26. 26.74 − 19 =
  27. 27.38 − 19 =
  28. 28.54 + 29 =
  29. 29.42 + 9 =
  30. 30.710 + 99 =
  31. 31.738 + 99 =
  32. 32.53 + 19 =
  33. 33.515 + 99 =
  34. 34.39 − 29 =
  35. 35.569 − 99 =
  36. 36.726 − 99 =
  37. 37.79 − 9 =
  38. 38.373 + 99 =
  39. 39.628 − 99 =
  40. 40.647 + 99 =

Answer key

  1. 36
  2. 91
  3. 40
  4. 41
  5. 44
  6. 57
  7. 46
  8. 342
  9. 17
  10. 619
  11. 58
  12. 75
  13. 90
  14. 16
  15. 43
  16. 77
  17. 83
  18. 73
  19. 296
  20. 37
  21. 48
  22. 67
  23. 52
  24. 42
  25. 33
  26. 55
  27. 19
  28. 83
  29. 51
  30. 809
  31. 837
  32. 72
  33. 614
  34. 10
  35. 470
  36. 627
  37. 70
  38. 472
  39. 529
  40. 746

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