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Nov 2018 p61 q7
2655
In a group of students, the numbers of boys and girls studying Art, Music and Drama are given in the following table. Each of these 160 students is studying exactly one of these subjects.
Art
Music
Drama
Boys
24
40
32
Girls
15
12
37
Find the probability that a randomly chosen student is studying Music.
Determine whether the events ‘a randomly chosen student is a boy’ and ‘a randomly chosen student is studying Music’ are independent, justifying your answer.
Solution
(i) The total number of students studying Music is \(40 + 12 = 52\). The total number of students is 160. Therefore, the probability that a randomly chosen student is studying Music is \(\frac{52}{160} = \frac{13}{40}\) or 0.325.
(ii) To determine independence, we check if \(P(\text{boy}) \times P(\text{Music}) = P(\text{boy and Music})\).
\(P(\text{boy}) = \frac{96}{160}\) since there are \(24 + 40 + 32 = 96\) boys.
\(P(\text{Music}) = \frac{52}{160}\) as calculated earlier.
\(P(\text{boy and Music}) = \frac{40}{160}\) since there are 40 boys studying Music.
Now, \(\frac{96}{160} \times \frac{52}{160} \neq \frac{40}{160}\), so the events are not independent.