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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 772 · 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. 1.32 + 29 =
  2. 2.34 + 29 =
  3. 3.13 + 29 =
  4. 4.61 − 29 =
  5. 5.65 + 9 =
  6. 6.32 − 9 =
  7. 7.29 − 9 =
  8. 8.28 + 19 =
  9. 9.68 − 19 =
  10. 10.36 − 19 =
  11. 11.24 − 19 =
  12. 12.738 + 99 =
  13. 13.27 − 9 =
  14. 14.80 + 9 =
  15. 15.147 + 99 =
  16. 16.36 + 19 =
  17. 17.64 + 19 =
  18. 18.468 + 99 =
  19. 19.582 + 99 =
  20. 20.29 + 19 =
  21. 21.20 + 19 =
  22. 22.105 − 29 =
  23. 23.652 + 99 =
  24. 24.51 − 19 =
  25. 25.44 − 29 =
  26. 26.17 + 29 =
  27. 27.21 − 9 =
  28. 28.44 + 9 =
  29. 29.83 − 29 =
  30. 30.74 + 9 =
  31. 31.92 − 19 =
  32. 32.70 + 9 =
  33. 33.704 + 99 =
  34. 34.64 + 9 =
  35. 35.39 + 19 =
  36. 36.42 + 29 =
  37. 37.63 − 19 =
  38. 38.15 − 9 =
  39. 39.612 + 99 =
  40. 40.50 − 29 =

Answer key

  1. 61
  2. 63
  3. 42
  4. 32
  5. 74
  6. 23
  7. 20
  8. 47
  9. 49
  10. 17
  11. 5
  12. 837
  13. 18
  14. 89
  15. 246
  16. 55
  17. 83
  18. 567
  19. 681
  20. 48
  21. 39
  22. 76
  23. 751
  24. 32
  25. 15
  26. 46
  27. 12
  28. 53
  29. 54
  30. 83
  31. 73
  32. 79
  33. 803
  34. 73
  35. 58
  36. 71
  37. 44
  38. 6
  39. 711
  40. 21

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