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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 729 · 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. 1.72 + 29 =
  2. 2.202 − 99 =
  3. 3.75 − 9 =
  4. 4.176 − 99 =
  5. 5.67 + 9 =
  6. 6.32 + 19 =
  7. 7.30 + 29 =
  8. 8.12 − 9 =
  9. 9.61 + 9 =
  10. 10.13 + 9 =
  11. 11.93 − 19 =
  12. 12.48 − 29 =
  13. 13.171 + 99 =
  14. 14.369 + 99 =
  15. 15.13 − 9 =
  16. 16.108 − 29 =
  17. 17.24 + 9 =
  18. 18.738 + 99 =
  19. 19.894 − 99 =
  20. 20.23 − 19 =
  21. 21.48 + 19 =
  22. 22.76 + 19 =
  23. 23.41 − 9 =
  24. 24.676 − 99 =
  25. 25.51 − 29 =
  26. 26.236 − 99 =
  27. 27.49 + 19 =
  28. 28.892 − 99 =
  29. 29.48 − 9 =
  30. 30.61 + 19 =
  31. 31.50 + 9 =
  32. 32.50 − 29 =
  33. 33.82 − 19 =
  34. 34.336 + 99 =
  35. 35.549 + 99 =
  36. 36.657 + 99 =
  37. 37.62 + 29 =
  38. 38.15 + 29 =
  39. 39.61 − 19 =
  40. 40.73 + 9 =

Answer key

  1. 101
  2. 103
  3. 66
  4. 77
  5. 76
  6. 51
  7. 59
  8. 3
  9. 70
  10. 22
  11. 74
  12. 19
  13. 270
  14. 468
  15. 4
  16. 79
  17. 33
  18. 837
  19. 795
  20. 4
  21. 67
  22. 95
  23. 32
  24. 577
  25. 22
  26. 137
  27. 68
  28. 793
  29. 39
  30. 80
  31. 59
  32. 21
  33. 63
  34. 435
  35. 648
  36. 756
  37. 91
  38. 44
  39. 42
  40. 82

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