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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 276 · 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. 1.33 + 29 =
  2. 2.513 + 99 =
  3. 3.52 − 19 =
  4. 4.51 + 19 =
  5. 5.23 + 29 =
  6. 6.745 − 99 =
  7. 7.69 + 9 =
  8. 8.75 + 9 =
  9. 9.61 + 9 =
  10. 10.155 + 99 =
  11. 11.38 − 9 =
  12. 12.38 + 9 =
  13. 13.17 + 9 =
  14. 14.281 − 99 =
  15. 15.534 + 99 =
  16. 16.12 − 9 =
  17. 17.36 − 29 =
  18. 18.15 + 29 =
  19. 19.28 + 19 =
  20. 20.303 − 99 =
  21. 21.514 − 99 =
  22. 22.37 − 9 =
  23. 23.31 + 29 =
  24. 24.24 + 29 =
  25. 25.77 − 9 =
  26. 26.545 − 99 =
  27. 27.78 + 19 =
  28. 28.23 + 9 =
  29. 29.887 − 99 =
  30. 30.34 + 9 =
  31. 31.721 + 99 =
  32. 32.51 − 29 =
  33. 33.407 − 99 =
  34. 34.24 − 19 =
  35. 35.597 + 99 =
  36. 36.779 + 99 =
  37. 37.40 − 9 =
  38. 38.57 + 9 =
  39. 39.45 − 29 =
  40. 40.71 + 19 =

Answer key

  1. 62
  2. 612
  3. 33
  4. 70
  5. 52
  6. 646
  7. 78
  8. 84
  9. 70
  10. 254
  11. 29
  12. 47
  13. 26
  14. 182
  15. 633
  16. 3
  17. 7
  18. 44
  19. 47
  20. 204
  21. 415
  22. 28
  23. 60
  24. 53
  25. 68
  26. 446
  27. 97
  28. 32
  29. 788
  30. 43
  31. 820
  32. 22
  33. 308
  34. 5
  35. 696
  36. 878
  37. 31
  38. 66
  39. 16
  40. 90

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