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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 941 · 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. 1.730 + 99 =
  2. 2.414 + 99 =
  3. 3.46 + 9 =
  4. 4.27 + 19 =
  5. 5.723 + 99 =
  6. 6.617 − 99 =
  7. 7.227 + 99 =
  8. 8.14 + 9 =
  9. 9.78 − 9 =
  10. 10.70 + 19 =
  11. 11.66 − 9 =
  12. 12.49 + 29 =
  13. 13.20 + 29 =
  14. 14.488 + 99 =
  15. 15.85 − 9 =
  16. 16.55 + 19 =
  17. 17.419 + 99 =
  18. 18.45 − 29 =
  19. 19.67 + 19 =
  20. 20.59 + 9 =
  21. 21.23 + 29 =
  22. 22.458 + 99 =
  23. 23.18 + 29 =
  24. 24.89 − 19 =
  25. 25.72 + 9 =
  26. 26.70 + 29 =
  27. 27.273 − 99 =
  28. 28.52 + 29 =
  29. 29.68 + 19 =
  30. 30.59 − 19 =
  31. 31.31 + 29 =
  32. 32.774 − 99 =
  33. 33.308 + 99 =
  34. 34.75 − 19 =
  35. 35.544 + 99 =
  36. 36.100 − 29 =
  37. 37.792 − 99 =
  38. 38.22 + 9 =
  39. 39.55 − 19 =
  40. 40.49 + 19 =

Answer key

  1. 829
  2. 513
  3. 55
  4. 46
  5. 822
  6. 518
  7. 326
  8. 23
  9. 69
  10. 89
  11. 57
  12. 78
  13. 49
  14. 587
  15. 76
  16. 74
  17. 518
  18. 16
  19. 86
  20. 68
  21. 52
  22. 557
  23. 47
  24. 70
  25. 81
  26. 99
  27. 174
  28. 81
  29. 87
  30. 40
  31. 60
  32. 675
  33. 407
  34. 56
  35. 643
  36. 71
  37. 693
  38. 31
  39. 36
  40. 68

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