For a group of 250 cars the numbers, classified by colour and country of manufacture, are shown in the table.
| Germany | Japan | Korea |
|---|
| Silver | 40 | 26 | 34 |
| White | 32 | 22 | 26 |
| Red | 28 | 12 | 30 |
One car is selected at random from this group. Find the probability that the selected car is
- a red or silver car manufactured in Korea,
- not manufactured in Japan.
X is the event that the selected car is white. Y is the event that the selected car is manufactured in Germany.
(iii) By using appropriate probabilities, determine whether events X and Y are independent.
Solution
(i) The number of red or silver cars manufactured in Korea is \(34 + 30 = 64\). The probability is \(\frac{64}{250} = 0.256\).
(ii) The number of cars not manufactured in Japan is \(250 - (26 + 22 + 12) = 190\). The probability is \(\frac{190}{250} = 0.76\).
(iii) Calculate \(P(X)\), \(P(Y)\), and \(P(X \cap Y)\):
\(P(X) = \frac{80}{250} = \frac{8}{25}\)
\(P(Y) = \frac{100}{250} = \frac{2}{5}\)
\(P(X \cap Y) = \frac{32}{250} = \frac{16}{125}\)
Check independence: \(P(X) \times P(Y) = \frac{8}{25} \times \frac{2}{5} = \frac{16}{125}\)
Since \(P(X) \times P(Y) = P(X \cap Y)\), events X and Y are independent.
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