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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 442 · 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. 1.27 − 19 =
  2. 2.12 − 9 =
  3. 3.15 + 9 =
  4. 4.71 + 19 =
  5. 5.67 + 19 =
  6. 6.34 + 9 =
  7. 7.787 − 99 =
  8. 8.79 − 19 =
  9. 9.43 − 19 =
  10. 10.29 + 29 =
  11. 11.38 + 29 =
  12. 12.60 − 9 =
  13. 13.71 + 9 =
  14. 14.39 − 9 =
  15. 15.37 − 19 =
  16. 16.36 + 9 =
  17. 17.75 + 29 =
  18. 18.36 − 29 =
  19. 19.850 − 99 =
  20. 20.74 − 19 =
  21. 21.68 − 19 =
  22. 22.23 − 9 =
  23. 23.31 + 29 =
  24. 24.408 − 99 =
  25. 25.26 + 9 =
  26. 26.52 − 19 =
  27. 27.52 + 9 =
  28. 28.44 + 29 =
  29. 29.81 − 19 =
  30. 30.31 − 9 =
  31. 31.64 − 19 =
  32. 32.211 − 99 =
  33. 33.57 − 29 =
  34. 34.385 + 99 =
  35. 35.887 − 99 =
  36. 36.45 − 29 =
  37. 37.484 − 99 =
  38. 38.88 − 29 =
  39. 39.53 + 19 =
  40. 40.68 + 19 =

Answer key

  1. 8
  2. 3
  3. 24
  4. 90
  5. 86
  6. 43
  7. 688
  8. 60
  9. 24
  10. 58
  11. 67
  12. 51
  13. 80
  14. 30
  15. 18
  16. 45
  17. 104
  18. 7
  19. 751
  20. 55
  21. 49
  22. 14
  23. 60
  24. 309
  25. 35
  26. 33
  27. 61
  28. 73
  29. 62
  30. 22
  31. 45
  32. 112
  33. 28
  34. 484
  35. 788
  36. 16
  37. 385
  38. 59
  39. 72
  40. 87

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