In a survey of 60 people, it was found that 25 people read newspaper H,
Question:

In a survey of 60 people, it was found that 25 people read newspaper H, 26 read newspaper T, 26 read newspaper I, 9 read both H and I, 11 read both H and T, 8 read both T and I, 3 read all three newspapers. Find:

(i) the numbers of people who read at least one of the newspapers.

(ii) the number of people who read exactly one newspaper.

Solution:

Given :

$n(H)=25$

$n(T)=26$

$n(I)=26$

$n(H \cap I)=9$

$n(H \cap T)=11$

$n(T \cap I)=8$

$n(H \cap T \cap I)=3$

(i) We know:

$n(H \cup T \cup I)=n(H)+n(T)+n(I)-n(H \cap T)-n(T \cap I)-n(H \cap I)+n(H \cap T \cap I)$

$\Rightarrow n(H \cup T \cup I)=25+26+26-11-8-9+3=52$

Thus, 52 people can read at least one of the newspapers.

(ii) Now, we have to calculate the number of people who read exactly one newspaper.

We have:

$n(H)+n(T)+n(I)-2 n(H \cap T)-2 n(T \cap I)-2 n(H \cap I)+3 n(H \cap T \cap I)$

$=25+26+26-22-16-18+9$

$=30$

Thus, 30 people can read exactly one newspaper.

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