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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 191 · 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. 1.31 + 9 =
  2. 2.44 − 29 =
  3. 3.37 + 9 =
  4. 4.12 + 19 =
  5. 5.51 + 29 =
  6. 6.82 − 29 =
  7. 7.32 + 19 =
  8. 8.179 + 99 =
  9. 9.66 + 19 =
  10. 10.716 + 99 =
  11. 11.39 − 29 =
  12. 12.254 − 99 =
  13. 13.83 − 9 =
  14. 14.42 + 19 =
  15. 15.30 + 9 =
  16. 16.61 + 29 =
  17. 17.78 − 29 =
  18. 18.47 − 29 =
  19. 19.74 + 29 =
  20. 20.34 + 9 =
  21. 21.719 + 99 =
  22. 22.58 + 29 =
  23. 23.48 + 19 =
  24. 24.67 − 19 =
  25. 25.68 + 29 =
  26. 26.22 − 9 =
  27. 27.39 + 9 =
  28. 28.38 + 9 =
  29. 29.61 − 19 =
  30. 30.419 − 99 =
  31. 31.57 + 19 =
  32. 32.41 + 19 =
  33. 33.95 − 19 =
  34. 34.87 − 19 =
  35. 35.80 − 29 =
  36. 36.400 − 99 =
  37. 37.39 − 19 =
  38. 38.52 − 29 =
  39. 39.693 − 99 =
  40. 40.40 + 9 =

Answer key

  1. 40
  2. 15
  3. 46
  4. 31
  5. 80
  6. 53
  7. 51
  8. 278
  9. 85
  10. 815
  11. 10
  12. 155
  13. 74
  14. 61
  15. 39
  16. 90
  17. 49
  18. 18
  19. 103
  20. 43
  21. 818
  22. 87
  23. 67
  24. 48
  25. 97
  26. 13
  27. 48
  28. 47
  29. 42
  30. 320
  31. 76
  32. 60
  33. 76
  34. 68
  35. 51
  36. 301
  37. 20
  38. 23
  39. 594
  40. 49

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