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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 923 · 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. 1.45 − 29 =
  2. 2.20 − 9 =
  3. 3.72 − 9 =
  4. 4.80 − 29 =
  5. 5.688 + 99 =
  6. 6.44 + 9 =
  7. 7.216 − 99 =
  8. 8.655 − 99 =
  9. 9.18 + 29 =
  10. 10.23 + 9 =
  11. 11.85 − 19 =
  12. 12.64 + 9 =
  13. 13.73 + 9 =
  14. 14.351 + 99 =
  15. 15.22 − 19 =
  16. 16.69 + 29 =
  17. 17.60 + 9 =
  18. 18.39 − 29 =
  19. 19.63 + 9 =
  20. 20.214 − 99 =
  21. 21.17 + 19 =
  22. 22.21 + 29 =
  23. 23.57 + 19 =
  24. 24.244 + 99 =
  25. 25.50 + 9 =
  26. 26.743 + 99 =
  27. 27.54 + 9 =
  28. 28.75 + 9 =
  29. 29.29 + 29 =
  30. 30.883 − 99 =
  31. 31.56 + 19 =
  32. 32.77 − 19 =
  33. 33.62 − 29 =
  34. 34.40 + 19 =
  35. 35.17 − 9 =
  36. 36.849 − 99 =
  37. 37.597 − 99 =
  38. 38.85 − 9 =
  39. 39.14 + 19 =
  40. 40.13 − 9 =

Answer key

  1. 16
  2. 11
  3. 63
  4. 51
  5. 787
  6. 53
  7. 117
  8. 556
  9. 47
  10. 32
  11. 66
  12. 73
  13. 82
  14. 450
  15. 3
  16. 98
  17. 69
  18. 10
  19. 72
  20. 115
  21. 36
  22. 50
  23. 76
  24. 343
  25. 59
  26. 842
  27. 63
  28. 84
  29. 58
  30. 784
  31. 75
  32. 58
  33. 33
  34. 59
  35. 8
  36. 750
  37. 498
  38. 76
  39. 33
  40. 4

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