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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 896 · 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. 1.48 − 19 =
  2. 2.696 + 99 =
  3. 3.35 − 9 =
  4. 4.14 + 19 =
  5. 5.26 + 9 =
  6. 6.89 − 19 =
  7. 7.23 − 9 =
  8. 8.125 + 99 =
  9. 9.246 − 99 =
  10. 10.44 + 9 =
  11. 11.116 + 99 =
  12. 12.38 − 9 =
  13. 13.73 + 19 =
  14. 14.586 + 99 =
  15. 15.66 + 19 =
  16. 16.481 − 99 =
  17. 17.20 + 29 =
  18. 18.58 + 9 =
  19. 19.89 − 9 =
  20. 20.63 + 19 =
  21. 21.48 − 29 =
  22. 22.75 + 29 =
  23. 23.828 − 99 =
  24. 24.189 + 99 =
  25. 25.76 − 29 =
  26. 26.58 − 9 =
  27. 27.35 + 9 =
  28. 28.56 − 9 =
  29. 29.76 + 9 =
  30. 30.70 + 9 =
  31. 31.14 + 9 =
  32. 32.33 − 29 =
  33. 33.51 − 9 =
  34. 34.46 + 19 =
  35. 35.813 − 99 =
  36. 36.19 + 19 =
  37. 37.234 − 99 =
  38. 38.12 + 9 =
  39. 39.65 + 19 =
  40. 40.618 + 99 =

Answer key

  1. 29
  2. 795
  3. 26
  4. 33
  5. 35
  6. 70
  7. 14
  8. 224
  9. 147
  10. 53
  11. 215
  12. 29
  13. 92
  14. 685
  15. 85
  16. 382
  17. 49
  18. 67
  19. 80
  20. 82
  21. 19
  22. 104
  23. 729
  24. 288
  25. 47
  26. 49
  27. 44
  28. 47
  29. 85
  30. 79
  31. 23
  32. 4
  33. 42
  34. 65
  35. 714
  36. 38
  37. 135
  38. 21
  39. 84
  40. 717

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