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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 124 · 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. 1.22 − 19 =
  2. 2.74 − 9 =
  3. 3.379 + 99 =
  4. 4.784 − 99 =
  5. 5.76 − 9 =
  6. 6.798 + 99 =
  7. 7.68 + 9 =
  8. 8.12 + 29 =
  9. 9.22 + 29 =
  10. 10.475 + 99 =
  11. 11.39 + 19 =
  12. 12.18 + 29 =
  13. 13.619 + 99 =
  14. 14.346 + 99 =
  15. 15.43 + 9 =
  16. 16.59 + 9 =
  17. 17.49 − 19 =
  18. 18.110 + 99 =
  19. 19.26 + 9 =
  20. 20.48 − 9 =
  21. 21.87 − 19 =
  22. 22.193 − 99 =
  23. 23.45 + 9 =
  24. 24.94 − 19 =
  25. 25.18 + 19 =
  26. 26.37 + 9 =
  27. 27.76 + 9 =
  28. 28.658 + 99 =
  29. 29.68 − 9 =
  30. 30.58 − 19 =
  31. 31.26 − 9 =
  32. 32.58 − 9 =
  33. 33.54 + 9 =
  34. 34.40 + 29 =
  35. 35.368 + 99 =
  36. 36.83 − 29 =
  37. 37.47 + 19 =
  38. 38.16 + 9 =
  39. 39.41 − 29 =
  40. 40.439 − 99 =

Answer key

  1. 3
  2. 65
  3. 478
  4. 685
  5. 67
  6. 897
  7. 77
  8. 41
  9. 51
  10. 574
  11. 58
  12. 47
  13. 718
  14. 445
  15. 52
  16. 68
  17. 30
  18. 209
  19. 35
  20. 39
  21. 68
  22. 94
  23. 54
  24. 75
  25. 37
  26. 46
  27. 85
  28. 757
  29. 59
  30. 39
  31. 17
  32. 49
  33. 63
  34. 69
  35. 467
  36. 54
  37. 66
  38. 25
  39. 12
  40. 340

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