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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 593 · 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. 1.98 − 19 =
  2. 2.312 − 99 =
  3. 3.720 + 99 =
  4. 4.26 + 9 =
  5. 5.68 − 9 =
  6. 6.614 + 99 =
  7. 7.44 − 19 =
  8. 8.765 − 99 =
  9. 9.58 − 9 =
  10. 10.792 + 99 =
  11. 11.72 + 29 =
  12. 12.28 + 9 =
  13. 13.40 − 19 =
  14. 14.30 + 29 =
  15. 15.538 − 99 =
  16. 16.89 − 9 =
  17. 17.67 + 29 =
  18. 18.42 + 9 =
  19. 19.368 − 99 =
  20. 20.239 + 99 =
  21. 21.818 − 99 =
  22. 22.77 + 29 =
  23. 23.42 + 19 =
  24. 24.36 − 9 =
  25. 25.30 + 19 =
  26. 26.429 + 99 =
  27. 27.31 − 9 =
  28. 28.757 + 99 =
  29. 29.33 + 19 =
  30. 30.250 − 99 =
  31. 31.64 − 29 =
  32. 32.46 + 19 =
  33. 33.41 + 9 =
  34. 34.93 − 19 =
  35. 35.41 − 29 =
  36. 36.31 + 19 =
  37. 37.68 + 19 =
  38. 38.70 − 29 =
  39. 39.12 + 19 =
  40. 40.55 + 19 =

Answer key

  1. 79
  2. 213
  3. 819
  4. 35
  5. 59
  6. 713
  7. 25
  8. 666
  9. 49
  10. 891
  11. 101
  12. 37
  13. 21
  14. 59
  15. 439
  16. 80
  17. 96
  18. 51
  19. 269
  20. 338
  21. 719
  22. 106
  23. 61
  24. 27
  25. 49
  26. 528
  27. 22
  28. 856
  29. 52
  30. 151
  31. 35
  32. 65
  33. 50
  34. 74
  35. 12
  36. 50
  37. 87
  38. 41
  39. 31
  40. 74

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