There are 10 rolls of film in a box and 3 are defective. Two rolls are to be selected one after the other. What is the probability of selecting a defective roll followed by another defective roll?
A) 1/2 or 0.50
B) 1/4 or 0.25
C) 1/120, or about 0.0083
D) 1/15, or about 0.07

Question

Quizplus · Accepted Answer

The probability of selecting a defective roll on the first draw is 3/10 since there are three defective rolls out of a total of ten.

After the first draw, there will be nine rolls left and two defective rolls remaining. Therefore, the probability of selecting another defective roll on the second draw is 2/9.

To calculate the probability of both events happening (selecting a defective roll followed by another defective roll), we need to multiply the probabilities of the two events.

So, the probability of selecting a defective roll followed by another defective roll is (3/10) x (2/9) = 6/90 = 1/15, or about 0.07.

Therefore, the best choice is D.

There Are 10 Rolls of Film in a Box and 3