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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 839 · 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. 1.30 + 9 =
  2. 2.62 − 19 =
  3. 3.826 − 99 =
  4. 4.58 − 19 =
  5. 5.318 − 99 =
  6. 6.51 − 9 =
  7. 7.17 + 19 =
  8. 8.673 − 99 =
  9. 9.69 − 29 =
  10. 10.14 + 19 =
  11. 11.392 + 99 =
  12. 12.55 + 9 =
  13. 13.695 − 99 =
  14. 14.21 + 29 =
  15. 15.60 + 9 =
  16. 16.32 + 29 =
  17. 17.42 − 19 =
  18. 18.47 − 9 =
  19. 19.92 − 29 =
  20. 20.78 − 9 =
  21. 21.24 + 9 =
  22. 22.18 + 9 =
  23. 23.412 + 99 =
  24. 24.676 − 99 =
  25. 25.27 + 29 =
  26. 26.51 + 9 =
  27. 27.706 − 99 =
  28. 28.258 − 99 =
  29. 29.360 − 99 =
  30. 30.66 + 19 =
  31. 31.14 + 9 =
  32. 32.59 − 19 =
  33. 33.631 + 99 =
  34. 34.33 − 19 =
  35. 35.69 + 29 =
  36. 36.26 + 9 =
  37. 37.739 − 99 =
  38. 38.722 − 99 =
  39. 39.36 − 19 =
  40. 40.30 + 19 =

Answer key

  1. 39
  2. 43
  3. 727
  4. 39
  5. 219
  6. 42
  7. 36
  8. 574
  9. 40
  10. 33
  11. 491
  12. 64
  13. 596
  14. 50
  15. 69
  16. 61
  17. 23
  18. 38
  19. 63
  20. 69
  21. 33
  22. 27
  23. 511
  24. 577
  25. 56
  26. 60
  27. 607
  28. 159
  29. 261
  30. 85
  31. 23
  32. 40
  33. 730
  34. 14
  35. 98
  36. 35
  37. 640
  38. 623
  39. 17
  40. 49

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