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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 56 · 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. 1.70 + 9 =
  2. 2.14 + 19 =
  3. 3.334 + 99 =
  4. 4.89 − 29 =
  5. 5.64 + 29 =
  6. 6.80 + 19 =
  7. 7.45 + 29 =
  8. 8.64 + 19 =
  9. 9.58 − 9 =
  10. 10.90 − 29 =
  11. 11.72 + 9 =
  12. 12.316 + 99 =
  13. 13.225 − 99 =
  14. 14.72 − 29 =
  15. 15.34 + 29 =
  16. 16.44 + 9 =
  17. 17.18 + 29 =
  18. 18.24 − 19 =
  19. 19.596 + 99 =
  20. 20.46 + 19 =
  21. 21.857 − 99 =
  22. 22.646 + 99 =
  23. 23.22 + 29 =
  24. 24.72 + 19 =
  25. 25.90 − 19 =
  26. 26.377 − 99 =
  27. 27.26 − 19 =
  28. 28.68 − 29 =
  29. 29.46 + 9 =
  30. 30.26 + 29 =
  31. 31.573 + 99 =
  32. 32.167 − 99 =
  33. 33.890 − 99 =
  34. 34.25 − 19 =
  35. 35.84 − 9 =
  36. 36.27 + 9 =
  37. 37.473 − 99 =
  38. 38.348 + 99 =
  39. 39.62 + 29 =
  40. 40.77 + 19 =

Answer key

  1. 79
  2. 33
  3. 433
  4. 60
  5. 93
  6. 99
  7. 74
  8. 83
  9. 49
  10. 61
  11. 81
  12. 415
  13. 126
  14. 43
  15. 63
  16. 53
  17. 47
  18. 5
  19. 695
  20. 65
  21. 758
  22. 745
  23. 51
  24. 91
  25. 71
  26. 278
  27. 7
  28. 39
  29. 55
  30. 55
  31. 672
  32. 68
  33. 791
  34. 6
  35. 75
  36. 36
  37. 374
  38. 447
  39. 91
  40. 96

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