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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 866 · 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. 1.66 − 9 =
  2. 2.462 + 99 =
  3. 3.17 + 19 =
  4. 4.12 + 19 =
  5. 5.66 + 29 =
  6. 6.50 + 9 =
  7. 7.213 + 99 =
  8. 8.37 + 29 =
  9. 9.880 − 99 =
  10. 10.58 + 29 =
  11. 11.776 + 99 =
  12. 12.23 + 19 =
  13. 13.413 + 99 =
  14. 14.82 − 19 =
  15. 15.63 + 19 =
  16. 16.47 + 19 =
  17. 17.55 − 29 =
  18. 18.19 + 9 =
  19. 19.33 + 19 =
  20. 20.779 − 99 =
  21. 21.89 − 19 =
  22. 22.62 + 9 =
  23. 23.17 + 9 =
  24. 24.716 + 99 =
  25. 25.20 + 29 =
  26. 26.80 − 9 =
  27. 27.82 − 29 =
  28. 28.52 + 29 =
  29. 29.40 − 19 =
  30. 30.81 − 9 =
  31. 31.77 + 9 =
  32. 32.68 − 29 =
  33. 33.16 + 9 =
  34. 34.15 + 19 =
  35. 35.24 + 9 =
  36. 36.69 + 9 =
  37. 37.208 − 99 =
  38. 38.14 + 19 =
  39. 39.320 + 99 =
  40. 40.249 + 99 =

Answer key

  1. 57
  2. 561
  3. 36
  4. 31
  5. 95
  6. 59
  7. 312
  8. 66
  9. 781
  10. 87
  11. 875
  12. 42
  13. 512
  14. 63
  15. 82
  16. 66
  17. 26
  18. 28
  19. 52
  20. 680
  21. 70
  22. 71
  23. 26
  24. 815
  25. 49
  26. 71
  27. 53
  28. 81
  29. 21
  30. 72
  31. 86
  32. 39
  33. 25
  34. 34
  35. 33
  36. 78
  37. 109
  38. 33
  39. 419
  40. 348

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