The probability of drawing a black marble from a bag is 1/2, and the probability of drawing a white marble from the same bag is 1/4. What is the probability of drawing a white marble, replacing it, and then drawing a black marble?

1/8

1/3

3/4

W = event where white marble is drawn

B = event where black marble is drawn

The two events W and B are independent. This is because the marble taken out on the first draw is put back into the bag. Since W and B are independent, we can use this rule

P (W and B) = P (w) * P (B)

Use the rule to get

P (W and B) = P (W) * P (B)

P (W and B) = (1/2) * (1/4)

P (W and B) = (1*1) / (2*4)

P (W and B) = 1/8

1/8 is equivalent to 0.125. Use long division or a calculator

0.125 = 12.5%

Answer is 1/8. this is because 1/2*1/4 equals 1/8.