Question

A jar of marbles contains $4$ blue, $5$ red, $1$ green and $2$ black marbles. A marble is chosen at random from the jar. After replacing it, a second marble is chosen. Find the probability of choosing a green and then a red marble.

• A. $\frac{3}{127}$
• B. $\frac{4}{37}$
• C. $\frac{5}{144}$
• D. None of these

Answer 1

Answer: (C)

$\frac{5}{144}$

The probability of choosing green marble as first marble is $\frac{1}{4+5+1+2}=\frac{1}{12}$

The green marble is replaced.

The probability of choosing red marble as second marble is $\frac{5}{4+5+1+2}=\frac{5}{12}$

The probability of choosing a green marble and then a red marble is $\frac{1}{12}\times \frac{5}{12}=\frac{5}{144}$