1) n(H U T U I) = n(H) + n(T) + n(I) - n(H ∩ T) - n(T ∩ I) - n(I ∩ H) + n(H ∩ T ∩ I)
==> n(H U T U I) = 25 + 26 + 26 - 11 - 8 - 9 + 3 = 52
==> Total number of people read one or more papers is 52.
But given survey is done among 60 people; so 8 of them do not read any of the papers mentioned.
2) Only n(H U T) = n(H ∩ T) - n(H ∩ T ∩ I)
==> Only n(H U T) = 11 - 3 = 8
Similalry Only n(T U I) = 8 - 3 = 5
and Only n(I U H) = 9 - 3 = 6
3) Thus from the above, number of persons reading either two or three papers =
= Only n(H U T) + Only n(T U I) + Only n(I U H) + n(H ∩ T ∩ I) = 8 + 5 + 6 + 3 = 22
4) So number of people reading only one paper = Total number of people reading one or more papers - number reading two or three papers
= 52 - 22 = 30
Thus number of people reading only one paper = 30
Alternatively, you may try to solve in another method also:
i) Number of people read only H = Total H - (H ∩ T) - (H ∩ I) + (H ∩ T ∩ I)
= 25 - 11 - 9 + 3 = 8
ii) NUmber of people read only T = 26 - 11 - 8 + 3 = 10
iii) Number of people read only I = 26 - 8 - 9 + 3 = 12
So total reading only one paper = 8 + 10 + 12 = 30
However of the above two, the best one to solve is with VENN Diagram, which you may try yourself.
