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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 188 · 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. 1.41 + 9 =
  2. 2.51 − 19 =
  3. 3.108 − 29 =
  4. 4.29 + 29 =
  5. 5.50 − 9 =
  6. 6.64 + 9 =
  7. 7.67 − 9 =
  8. 8.53 + 19 =
  9. 9.13 + 19 =
  10. 10.13 + 9 =
  11. 11.14 + 9 =
  12. 12.65 − 9 =
  13. 13.42 − 19 =
  14. 14.58 + 19 =
  15. 15.16 + 9 =
  16. 16.84 − 9 =
  17. 17.73 − 29 =
  18. 18.543 − 99 =
  19. 19.221 − 99 =
  20. 20.54 − 19 =
  21. 21.76 − 19 =
  22. 22.14 + 29 =
  23. 23.283 − 99 =
  24. 24.379 + 99 =
  25. 25.46 − 9 =
  26. 26.498 − 99 =
  27. 27.98 − 29 =
  28. 28.139 + 99 =
  29. 29.57 − 29 =
  30. 30.28 + 19 =
  31. 31.42 + 19 =
  32. 32.78 + 9 =
  33. 33.38 − 19 =
  34. 34.34 + 19 =
  35. 35.32 + 19 =
  36. 36.73 − 9 =
  37. 37.798 − 99 =
  38. 38.41 + 29 =
  39. 39.587 + 99 =
  40. 40.51 − 29 =

Answer key

  1. 50
  2. 32
  3. 79
  4. 58
  5. 41
  6. 73
  7. 58
  8. 72
  9. 32
  10. 22
  11. 23
  12. 56
  13. 23
  14. 77
  15. 25
  16. 75
  17. 44
  18. 444
  19. 122
  20. 35
  21. 57
  22. 43
  23. 184
  24. 478
  25. 37
  26. 399
  27. 69
  28. 238
  29. 28
  30. 47
  31. 61
  32. 87
  33. 19
  34. 53
  35. 51
  36. 64
  37. 699
  38. 70
  39. 686
  40. 22

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