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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 249 · 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. 1.44 + 19 =
  2. 2.775 + 99 =
  3. 3.33 + 29 =
  4. 4.31 − 9 =
  5. 5.95 − 29 =
  6. 6.57 − 19 =
  7. 7.70 + 9 =
  8. 8.661 − 99 =
  9. 9.26 − 9 =
  10. 10.738 + 99 =
  11. 11.101 − 29 =
  12. 12.579 − 99 =
  13. 13.539 − 99 =
  14. 14.44 − 29 =
  15. 15.22 − 19 =
  16. 16.97 − 19 =
  17. 17.43 − 29 =
  18. 18.39 + 19 =
  19. 19.49 + 9 =
  20. 20.36 − 19 =
  21. 21.81 − 9 =
  22. 22.50 + 29 =
  23. 23.767 + 99 =
  24. 24.714 + 99 =
  25. 25.20 − 9 =
  26. 26.38 − 29 =
  27. 27.30 − 9 =
  28. 28.885 − 99 =
  29. 29.28 + 9 =
  30. 30.69 + 29 =
  31. 31.42 + 9 =
  32. 32.76 − 19 =
  33. 33.69 − 9 =
  34. 34.166 − 99 =
  35. 35.23 − 9 =
  36. 36.12 + 9 =
  37. 37.14 + 9 =
  38. 38.89 − 19 =
  39. 39.80 + 19 =
  40. 40.20 + 29 =

Answer key

  1. 63
  2. 874
  3. 62
  4. 22
  5. 66
  6. 38
  7. 79
  8. 562
  9. 17
  10. 837
  11. 72
  12. 480
  13. 440
  14. 15
  15. 3
  16. 78
  17. 14
  18. 58
  19. 58
  20. 17
  21. 72
  22. 79
  23. 866
  24. 813
  25. 11
  26. 9
  27. 21
  28. 786
  29. 37
  30. 98
  31. 51
  32. 57
  33. 60
  34. 67
  35. 14
  36. 21
  37. 23
  38. 70
  39. 99
  40. 49

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