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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 796 · 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. 1.38 − 9 =
  2. 2.78 + 9 =
  3. 3.61 − 9 =
  4. 4.55 − 19 =
  5. 5.70 + 9 =
  6. 6.372 + 99 =
  7. 7.677 + 99 =
  8. 8.774 − 99 =
  9. 9.32 + 29 =
  10. 10.554 − 99 =
  11. 11.98 − 19 =
  12. 12.20 + 19 =
  13. 13.24 + 29 =
  14. 14.14 + 9 =
  15. 15.24 + 19 =
  16. 16.73 + 29 =
  17. 17.568 + 99 =
  18. 18.481 + 99 =
  19. 19.651 − 99 =
  20. 20.42 − 9 =
  21. 21.34 − 9 =
  22. 22.25 − 9 =
  23. 23.740 − 99 =
  24. 24.276 − 99 =
  25. 25.737 + 99 =
  26. 26.68 + 29 =
  27. 27.619 + 99 =
  28. 28.111 + 99 =
  29. 29.59 − 9 =
  30. 30.41 − 9 =
  31. 31.49 − 9 =
  32. 32.136 + 99 =
  33. 33.37 + 29 =
  34. 34.69 + 29 =
  35. 35.508 − 99 =
  36. 36.72 + 9 =
  37. 37.31 − 9 =
  38. 38.26 + 9 =
  39. 39.75 + 19 =
  40. 40.713 − 99 =

Answer key

  1. 29
  2. 87
  3. 52
  4. 36
  5. 79
  6. 471
  7. 776
  8. 675
  9. 61
  10. 455
  11. 79
  12. 39
  13. 53
  14. 23
  15. 43
  16. 102
  17. 667
  18. 580
  19. 552
  20. 33
  21. 25
  22. 16
  23. 641
  24. 177
  25. 836
  26. 97
  27. 718
  28. 210
  29. 50
  30. 32
  31. 40
  32. 235
  33. 66
  34. 98
  35. 409
  36. 81
  37. 22
  38. 35
  39. 94
  40. 614

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