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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 125 · 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. 1.31 + 19 =
  2. 2.57 − 29 =
  3. 3.59 − 9 =
  4. 4.13 + 9 =
  5. 5.33 + 19 =
  6. 6.627 − 99 =
  7. 7.94 − 29 =
  8. 8.655 + 99 =
  9. 9.27 + 19 =
  10. 10.36 − 19 =
  11. 11.22 − 19 =
  12. 12.56 + 9 =
  13. 13.17 + 19 =
  14. 14.467 + 99 =
  15. 15.775 + 99 =
  16. 16.19 − 9 =
  17. 17.15 + 29 =
  18. 18.162 − 99 =
  19. 19.15 − 9 =
  20. 20.91 − 19 =
  21. 21.29 − 9 =
  22. 22.86 − 19 =
  23. 23.19 + 19 =
  24. 24.60 + 9 =
  25. 25.40 − 29 =
  26. 26.213 + 99 =
  27. 27.93 − 29 =
  28. 28.285 + 99 =
  29. 29.14 + 29 =
  30. 30.91 − 29 =
  31. 31.46 − 9 =
  32. 32.41 + 9 =
  33. 33.76 + 29 =
  34. 34.23 − 9 =
  35. 35.38 − 9 =
  36. 36.36 + 19 =
  37. 37.47 + 29 =
  38. 38.23 + 19 =
  39. 39.60 − 19 =
  40. 40.15 + 19 =

Answer key

  1. 50
  2. 28
  3. 50
  4. 22
  5. 52
  6. 528
  7. 65
  8. 754
  9. 46
  10. 17
  11. 3
  12. 65
  13. 36
  14. 566
  15. 874
  16. 10
  17. 44
  18. 63
  19. 6
  20. 72
  21. 20
  22. 67
  23. 38
  24. 69
  25. 11
  26. 312
  27. 64
  28. 384
  29. 43
  30. 62
  31. 37
  32. 50
  33. 105
  34. 14
  35. 29
  36. 55
  37. 76
  38. 42
  39. 41
  40. 34

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