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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 831 · 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. 1.509 − 99 =
  2. 2.74 − 19 =
  3. 3.58 − 9 =
  4. 4.29 + 19 =
  5. 5.68 + 19 =
  6. 6.60 + 19 =
  7. 7.98 − 19 =
  8. 8.80 − 19 =
  9. 9.242 + 99 =
  10. 10.771 + 99 =
  11. 11.568 + 99 =
  12. 12.78 + 9 =
  13. 13.12 − 9 =
  14. 14.44 + 29 =
  15. 15.66 − 19 =
  16. 16.41 + 19 =
  17. 17.42 + 19 =
  18. 18.34 − 29 =
  19. 19.789 − 99 =
  20. 20.14 + 19 =
  21. 21.24 − 9 =
  22. 22.31 + 29 =
  23. 23.23 − 9 =
  24. 24.709 − 99 =
  25. 25.60 − 9 =
  26. 26.191 − 99 =
  27. 27.52 + 9 =
  28. 28.75 − 29 =
  29. 29.667 + 99 =
  30. 30.34 + 9 =
  31. 31.73 + 29 =
  32. 32.28 − 9 =
  33. 33.158 + 99 =
  34. 34.33 + 29 =
  35. 35.50 + 9 =
  36. 36.37 + 9 =
  37. 37.50 + 19 =
  38. 38.67 + 9 =
  39. 39.29 + 29 =
  40. 40.20 + 29 =

Answer key

  1. 410
  2. 55
  3. 49
  4. 48
  5. 87
  6. 79
  7. 79
  8. 61
  9. 341
  10. 870
  11. 667
  12. 87
  13. 3
  14. 73
  15. 47
  16. 60
  17. 61
  18. 5
  19. 690
  20. 33
  21. 15
  22. 60
  23. 14
  24. 610
  25. 51
  26. 92
  27. 61
  28. 46
  29. 766
  30. 43
  31. 102
  32. 19
  33. 257
  34. 62
  35. 59
  36. 46
  37. 69
  38. 76
  39. 58
  40. 49

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