Question

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. 1/120, or about 0.0083
B. 1/2 or 0.50
C. 1/120, or about 0.0083
D. 1/2 or 0.50
E. 1/4 or 0.25
F. 1/15, or about 0.07

Answer 1

The probability of selecting a defective roll followed by another defective roll is 1/15 or approximately 0.07.

Step-by-step explanation:

To determine the probability of selecting a defective roll followed by another defective roll, we need to consider the total number of rolls and the number of defective rolls. There are 10 rolls in total and 3 of them are defective.

For the first roll, the probability of selecting a defective roll is 3/10 (3 defective rolls out of 10 total rolls).

For the second roll, since one roll has already been selected and not replaced, there are now 9 rolls left and 2 of them are defective. Therefore, the probability of selecting another defective roll is 2/9.

To find the probability of both events occurring, we multiply the probabilities together:

P(defective roll followed by another defective roll) = (3/10) * (2/9) = 6/90 = 1/15 approximately 0.07