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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 335 · 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. 1.34 + 19 =
  2. 2.245 + 99 =
  3. 3.71 + 9 =
  4. 4.95 − 19 =
  5. 5.47 + 29 =
  6. 6.83 − 29 =
  7. 7.887 − 99 =
  8. 8.58 + 19 =
  9. 9.61 + 19 =
  10. 10.75 − 19 =
  11. 11.70 − 9 =
  12. 12.75 + 19 =
  13. 13.26 + 9 =
  14. 14.17 + 19 =
  15. 15.43 − 9 =
  16. 16.77 + 29 =
  17. 17.87 − 19 =
  18. 18.72 − 9 =
  19. 19.74 − 29 =
  20. 20.566 + 99 =
  21. 21.19 + 9 =
  22. 22.208 + 99 =
  23. 23.55 − 9 =
  24. 24.82 − 29 =
  25. 25.36 + 19 =
  26. 26.543 − 99 =
  27. 27.608 − 99 =
  28. 28.78 + 19 =
  29. 29.35 + 9 =
  30. 30.41 + 9 =
  31. 31.26 + 19 =
  32. 32.25 − 9 =
  33. 33.68 − 29 =
  34. 34.38 − 29 =
  35. 35.50 + 19 =
  36. 36.22 + 29 =
  37. 37.29 + 29 =
  38. 38.47 + 19 =
  39. 39.94 − 29 =
  40. 40.26 + 29 =

Answer key

  1. 53
  2. 344
  3. 80
  4. 76
  5. 76
  6. 54
  7. 788
  8. 77
  9. 80
  10. 56
  11. 61
  12. 94
  13. 35
  14. 36
  15. 34
  16. 106
  17. 68
  18. 63
  19. 45
  20. 665
  21. 28
  22. 307
  23. 46
  24. 53
  25. 55
  26. 444
  27. 509
  28. 97
  29. 44
  30. 50
  31. 45
  32. 16
  33. 39
  34. 9
  35. 69
  36. 51
  37. 58
  38. 66
  39. 65
  40. 55

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