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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 736 · 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. 1.92 − 19 =
  2. 2.562 − 99 =
  3. 3.72 + 9 =
  4. 4.79 + 9 =
  5. 5.67 − 9 =
  6. 6.177 + 99 =
  7. 7.33 − 9 =
  8. 8.64 + 9 =
  9. 9.63 + 19 =
  10. 10.713 + 99 =
  11. 11.73 − 29 =
  12. 12.341 − 99 =
  13. 13.73 + 19 =
  14. 14.18 + 9 =
  15. 15.71 − 29 =
  16. 16.660 + 99 =
  17. 17.476 − 99 =
  18. 18.52 + 9 =
  19. 19.45 − 9 =
  20. 20.31 + 9 =
  21. 21.81 − 19 =
  22. 22.68 − 19 =
  23. 23.13 + 29 =
  24. 24.50 − 9 =
  25. 25.15 + 29 =
  26. 26.162 + 99 =
  27. 27.50 − 19 =
  28. 28.59 + 29 =
  29. 29.69 + 29 =
  30. 30.671 + 99 =
  31. 31.82 − 9 =
  32. 32.191 − 99 =
  33. 33.560 − 99 =
  34. 34.53 + 29 =
  35. 35.32 − 19 =
  36. 36.520 + 99 =
  37. 37.83 − 19 =
  38. 38.23 + 9 =
  39. 39.402 + 99 =
  40. 40.23 + 29 =

Answer key

  1. 73
  2. 463
  3. 81
  4. 88
  5. 58
  6. 276
  7. 24
  8. 73
  9. 82
  10. 812
  11. 44
  12. 242
  13. 92
  14. 27
  15. 42
  16. 759
  17. 377
  18. 61
  19. 36
  20. 40
  21. 62
  22. 49
  23. 42
  24. 41
  25. 44
  26. 261
  27. 31
  28. 88
  29. 98
  30. 770
  31. 73
  32. 92
  33. 461
  34. 82
  35. 13
  36. 619
  37. 64
  38. 32
  39. 501
  40. 52

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