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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 303 · 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. 1.252 + 99 =
  2. 2.590 + 99 =
  3. 3.46 − 19 =
  4. 4.61 + 9 =
  5. 5.695 + 99 =
  6. 6.44 − 9 =
  7. 7.71 − 9 =
  8. 8.68 − 19 =
  9. 9.409 + 99 =
  10. 10.64 + 29 =
  11. 11.59 + 29 =
  12. 12.78 − 19 =
  13. 13.69 − 9 =
  14. 14.27 + 29 =
  15. 15.92 − 29 =
  16. 16.50 + 9 =
  17. 17.306 + 99 =
  18. 18.22 + 29 =
  19. 19.29 + 29 =
  20. 20.242 + 99 =
  21. 21.34 − 29 =
  22. 22.109 − 29 =
  23. 23.60 + 9 =
  24. 24.33 + 29 =
  25. 25.17 + 19 =
  26. 26.76 + 19 =
  27. 27.72 + 19 =
  28. 28.416 − 99 =
  29. 29.48 − 9 =
  30. 30.15 + 9 =
  31. 31.41 + 29 =
  32. 32.72 − 29 =
  33. 33.37 + 29 =
  34. 34.174 + 99 =
  35. 35.102 − 29 =
  36. 36.569 − 99 =
  37. 37.79 + 19 =
  38. 38.22 + 9 =
  39. 39.751 − 99 =
  40. 40.24 + 29 =

Answer key

  1. 351
  2. 689
  3. 27
  4. 70
  5. 794
  6. 35
  7. 62
  8. 49
  9. 508
  10. 93
  11. 88
  12. 59
  13. 60
  14. 56
  15. 63
  16. 59
  17. 405
  18. 51
  19. 58
  20. 341
  21. 5
  22. 80
  23. 69
  24. 62
  25. 36
  26. 95
  27. 91
  28. 317
  29. 39
  30. 24
  31. 70
  32. 43
  33. 66
  34. 273
  35. 73
  36. 470
  37. 98
  38. 31
  39. 652
  40. 53

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