Question

a bag contains 18 red marbles, 6 white marbles, and 3 gray marbles. you randomly pick out a marble, record its color, and put it back in the bag. you repeat this process 81 times. how many white or gray marbles do you expect to get?
if you randomly pick out a marble and replace it 81 times, you can expect \boxed{} white or gray marbles to be chosen.

Explanation:

Step1: Calculate total marbles

$18 + 6 + 3 = 27$

Step2: Find favorable marble count

$6 + 3 = 9$

Step3: Compute success probability

$\frac{9}{27} = \frac{1}{3}$

Step4: Calculate expected value

$81 \times \frac{1}{3} = 27$

Answer:

27