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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 165 · 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. 1.66 + 9 =
  2. 2.79 − 9 =
  3. 3.32 + 9 =
  4. 4.316 + 99 =
  5. 5.746 + 99 =
  6. 6.30 − 19 =
  7. 7.52 + 9 =
  8. 8.77 + 29 =
  9. 9.40 − 9 =
  10. 10.425 + 99 =
  11. 11.724 − 99 =
  12. 12.26 + 9 =
  13. 13.64 − 9 =
  14. 14.761 + 99 =
  15. 15.74 − 9 =
  16. 16.36 − 9 =
  17. 17.60 − 9 =
  18. 18.40 − 29 =
  19. 19.58 + 19 =
  20. 20.64 − 19 =
  21. 21.602 − 99 =
  22. 22.44 + 19 =
  23. 23.74 − 29 =
  24. 24.71 − 9 =
  25. 25.98 − 29 =
  26. 26.498 − 99 =
  27. 27.505 + 99 =
  28. 28.222 − 99 =
  29. 29.199 − 99 =
  30. 30.41 + 19 =
  31. 31.32 − 9 =
  32. 32.235 + 99 =
  33. 33.61 + 9 =
  34. 34.356 + 99 =
  35. 35.256 − 99 =
  36. 36.23 + 19 =
  37. 37.75 − 9 =
  38. 38.41 + 9 =
  39. 39.570 − 99 =
  40. 40.288 + 99 =

Answer key

  1. 75
  2. 70
  3. 41
  4. 415
  5. 845
  6. 11
  7. 61
  8. 106
  9. 31
  10. 524
  11. 625
  12. 35
  13. 55
  14. 860
  15. 65
  16. 27
  17. 51
  18. 11
  19. 77
  20. 45
  21. 503
  22. 63
  23. 45
  24. 62
  25. 69
  26. 399
  27. 604
  28. 123
  29. 100
  30. 60
  31. 23
  32. 334
  33. 70
  34. 455
  35. 157
  36. 42
  37. 66
  38. 50
  39. 471
  40. 387

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