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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 874 · 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. 1.68 − 9 =
  2. 2.44 − 9 =
  3. 3.45 + 9 =
  4. 4.67 − 19 =
  5. 5.38 − 9 =
  6. 6.101 − 29 =
  7. 7.37 − 29 =
  8. 8.75 − 29 =
  9. 9.146 + 99 =
  10. 10.65 − 29 =
  11. 11.27 − 9 =
  12. 12.60 + 19 =
  13. 13.50 + 19 =
  14. 14.69 + 9 =
  15. 15.37 + 9 =
  16. 16.25 + 19 =
  17. 17.36 − 9 =
  18. 18.41 + 19 =
  19. 19.39 + 19 =
  20. 20.29 + 9 =
  21. 21.22 + 9 =
  22. 22.56 − 19 =
  23. 23.69 + 29 =
  24. 24.717 + 99 =
  25. 25.13 − 9 =
  26. 26.41 − 19 =
  27. 27.393 − 99 =
  28. 28.92 − 29 =
  29. 29.104 − 29 =
  30. 30.83 − 19 =
  31. 31.34 + 19 =
  32. 32.123 + 99 =
  33. 33.22 + 19 =
  34. 34.29 + 19 =
  35. 35.68 − 29 =
  36. 36.630 − 99 =
  37. 37.690 + 99 =
  38. 38.63 + 9 =
  39. 39.331 − 99 =
  40. 40.49 + 29 =

Answer key

  1. 59
  2. 35
  3. 54
  4. 48
  5. 29
  6. 72
  7. 8
  8. 46
  9. 245
  10. 36
  11. 18
  12. 79
  13. 69
  14. 78
  15. 46
  16. 44
  17. 27
  18. 60
  19. 58
  20. 38
  21. 31
  22. 37
  23. 98
  24. 816
  25. 4
  26. 22
  27. 294
  28. 63
  29. 75
  30. 64
  31. 53
  32. 222
  33. 41
  34. 48
  35. 39
  36. 531
  37. 789
  38. 72
  39. 232
  40. 78

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