Question

A jar contains five red marbles and three green marbles. A marble is drawn at random and not replaced. A second marble is then drawn from the jar. Find the probability that the first marble is red and the second marble is green.

Answer 1

Probablility that that first marble is red:
$P_{red} = \frac{red}{total}$
$P_{red} = \frac{5}{5+3}$

Probability that the second marble is green:
$P_{green} = \frac{green}{total(new)}$
$P_{green}= \frac{3}{4+3}$ (because 1 red is now gone)

$P_{total}=P_{red} \times P_{green}$
$P_{total}= \frac{6}{8} \times \frac{3}{7} = \frac{18}{56} = \frac{9}{28} \approx 32.1\%$