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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 403 · 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. 1.43 + 29 =
  2. 2.756 − 99 =
  3. 3.54 − 9 =
  4. 4.136 + 99 =
  5. 5.79 + 9 =
  6. 6.79 − 29 =
  7. 7.12 + 19 =
  8. 8.16 + 29 =
  9. 9.84 − 9 =
  10. 10.31 − 19 =
  11. 11.75 − 9 =
  12. 12.151 + 99 =
  13. 13.62 + 19 =
  14. 14.63 − 19 =
  15. 15.77 − 9 =
  16. 16.52 + 29 =
  17. 17.53 + 19 =
  18. 18.30 − 19 =
  19. 19.22 + 29 =
  20. 20.64 + 29 =
  21. 21.66 − 19 =
  22. 22.668 − 99 =
  23. 23.54 − 19 =
  24. 24.41 + 29 =
  25. 25.318 + 99 =
  26. 26.20 − 9 =
  27. 27.46 + 29 =
  28. 28.99 − 19 =
  29. 29.26 + 19 =
  30. 30.819 − 99 =
  31. 31.57 − 29 =
  32. 32.39 − 19 =
  33. 33.28 − 9 =
  34. 34.33 − 29 =
  35. 35.639 + 99 =
  36. 36.67 + 19 =
  37. 37.148 + 99 =
  38. 38.34 + 19 =
  39. 39.36 − 19 =
  40. 40.75 + 9 =

Answer key

  1. 72
  2. 657
  3. 45
  4. 235
  5. 88
  6. 50
  7. 31
  8. 45
  9. 75
  10. 12
  11. 66
  12. 250
  13. 81
  14. 44
  15. 68
  16. 81
  17. 72
  18. 11
  19. 51
  20. 93
  21. 47
  22. 569
  23. 35
  24. 70
  25. 417
  26. 11
  27. 75
  28. 80
  29. 45
  30. 720
  31. 28
  32. 20
  33. 19
  34. 4
  35. 738
  36. 86
  37. 247
  38. 53
  39. 17
  40. 84

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