Question

A ball is selected at random from a bag containing three red balls, four black balls and five green bars. The first ball is replaced and a second is selected. Find the probability of obtaining two red balls.

Answer 1

There are a total of $3+4+5=12$

The probability of picking one red ball is $\frac{3}{12}= \frac{1}{4}$ . Since the first ball is replaced, the probability of picking a red ball during the second picking is $\frac{1}{4}$

Thus, the probability of picking two red balls with replacement is $\frac{1}{4}×\frac{1}{4}= \frac{1}{16}$