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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 781 · 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. 1.409 − 99 =
  2. 2.39 + 19 =
  3. 3.80 + 19 =
  4. 4.62 + 9 =
  5. 5.16 + 9 =
  6. 6.839 − 99 =
  7. 7.51 − 19 =
  8. 8.67 − 19 =
  9. 9.84 − 9 =
  10. 10.26 + 29 =
  11. 11.49 − 29 =
  12. 12.17 + 19 =
  13. 13.447 + 99 =
  14. 14.42 − 9 =
  15. 15.13 − 9 =
  16. 16.32 + 29 =
  17. 17.73 − 29 =
  18. 18.36 + 9 =
  19. 19.566 + 99 =
  20. 20.77 + 9 =
  21. 21.67 + 19 =
  22. 22.29 + 19 =
  23. 23.23 − 19 =
  24. 24.15 + 9 =
  25. 25.668 − 99 =
  26. 26.77 − 9 =
  27. 27.60 + 9 =
  28. 28.32 − 9 =
  29. 29.854 − 99 =
  30. 30.22 + 9 =
  31. 31.770 − 99 =
  32. 32.65 − 9 =
  33. 33.230 + 99 =
  34. 34.69 + 9 =
  35. 35.88 − 19 =
  36. 36.158 + 99 =
  37. 37.53 − 9 =
  38. 38.644 + 99 =
  39. 39.380 − 99 =
  40. 40.43 − 19 =

Answer key

  1. 310
  2. 58
  3. 99
  4. 71
  5. 25
  6. 740
  7. 32
  8. 48
  9. 75
  10. 55
  11. 20
  12. 36
  13. 546
  14. 33
  15. 4
  16. 61
  17. 44
  18. 45
  19. 665
  20. 86
  21. 86
  22. 48
  23. 4
  24. 24
  25. 569
  26. 68
  27. 69
  28. 23
  29. 755
  30. 31
  31. 671
  32. 56
  33. 329
  34. 78
  35. 69
  36. 257
  37. 44
  38. 743
  39. 281
  40. 24

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