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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 913 · 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. 1.60 + 19 =
  2. 2.31 + 19 =
  3. 3.94 − 29 =
  4. 4.29 + 9 =
  5. 5.542 − 99 =
  6. 6.40 + 19 =
  7. 7.225 + 99 =
  8. 8.683 + 99 =
  9. 9.86 − 19 =
  10. 10.49 − 29 =
  11. 11.543 + 99 =
  12. 12.31 + 9 =
  13. 13.73 − 19 =
  14. 14.74 − 19 =
  15. 15.561 + 99 =
  16. 16.89 − 19 =
  17. 17.207 + 99 =
  18. 18.58 + 9 =
  19. 19.92 − 29 =
  20. 20.417 + 99 =
  21. 21.462 + 99 =
  22. 22.91 − 29 =
  23. 23.39 − 19 =
  24. 24.45 + 9 =
  25. 25.59 − 19 =
  26. 26.72 + 19 =
  27. 27.47 − 19 =
  28. 28.23 + 29 =
  29. 29.73 + 29 =
  30. 30.24 + 9 =
  31. 31.26 + 19 =
  32. 32.40 + 9 =
  33. 33.66 + 29 =
  34. 34.36 + 19 =
  35. 35.863 − 99 =
  36. 36.777 − 99 =
  37. 37.29 + 19 =
  38. 38.47 − 29 =
  39. 39.85 − 9 =
  40. 40.46 + 29 =

Answer key

  1. 79
  2. 50
  3. 65
  4. 38
  5. 443
  6. 59
  7. 324
  8. 782
  9. 67
  10. 20
  11. 642
  12. 40
  13. 54
  14. 55
  15. 660
  16. 70
  17. 306
  18. 67
  19. 63
  20. 516
  21. 561
  22. 62
  23. 20
  24. 54
  25. 40
  26. 91
  27. 28
  28. 52
  29. 102
  30. 33
  31. 45
  32. 49
  33. 95
  34. 55
  35. 764
  36. 678
  37. 48
  38. 18
  39. 76
  40. 75

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