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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 892 · 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. 1.639 + 99 =
  2. 2.49 + 29 =
  3. 3.30 + 9 =
  4. 4.81 − 29 =
  5. 5.88 − 19 =
  6. 6.27 − 9 =
  7. 7.292 − 99 =
  8. 8.13 + 19 =
  9. 9.40 − 19 =
  10. 10.237 − 99 =
  11. 11.39 + 9 =
  12. 12.245 + 99 =
  13. 13.44 + 19 =
  14. 14.41 + 19 =
  15. 15.33 + 9 =
  16. 16.34 − 19 =
  17. 17.17 + 19 =
  18. 18.778 + 99 =
  19. 19.629 − 99 =
  20. 20.166 − 99 =
  21. 21.45 + 9 =
  22. 22.729 + 99 =
  23. 23.60 − 19 =
  24. 24.52 − 9 =
  25. 25.667 − 99 =
  26. 26.650 − 99 =
  27. 27.145 + 99 =
  28. 28.71 − 19 =
  29. 29.98 − 19 =
  30. 30.452 − 99 =
  31. 31.891 − 99 =
  32. 32.12 + 29 =
  33. 33.13 + 9 =
  34. 34.89 − 29 =
  35. 35.19 + 9 =
  36. 36.69 + 19 =
  37. 37.80 − 29 =
  38. 38.78 − 9 =
  39. 39.413 − 99 =
  40. 40.49 + 9 =

Answer key

  1. 738
  2. 78
  3. 39
  4. 52
  5. 69
  6. 18
  7. 193
  8. 32
  9. 21
  10. 138
  11. 48
  12. 344
  13. 63
  14. 60
  15. 42
  16. 15
  17. 36
  18. 877
  19. 530
  20. 67
  21. 54
  22. 828
  23. 41
  24. 43
  25. 568
  26. 551
  27. 244
  28. 52
  29. 79
  30. 353
  31. 792
  32. 41
  33. 22
  34. 60
  35. 28
  36. 88
  37. 51
  38. 69
  39. 314
  40. 58

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