A bag contains 5 black and 4 white balls. A man selects two balls at random. What is the probability that both of these are of the same colour?
- AOption (a)
\(\frac{1}{6}\)
- BOption (b)
\(\frac{5}{108}\)
- COption (c)
\(\frac{4}{9}\)
- DOption (d)
\(\frac{5}{18}\)
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Correct answer
\(\frac{4}{9}\)
Why this answer is correct
Calculation:
Given, bag contains 5 black and 4 white balls.
A man selects two balls at random.
∴ P(both are of same colour)
= P(first ball is black)P(second ball is black) + P(first ball is white)P(seconf ball is white)
= \(\frac{5}{9}\times\frac{4}{8}+\frac{4}{9}\times\frac{3}{8}\)
= \(\frac{32}{72}\)
= \(\frac{4}{9}\)
∴ The probability that both of these are of the same colour is \(\frac{4}{9}\).
The correct answer is Option 3.