Question

Each of 11 refrigerators of a certain type has been returned to a distributor because of an audible, high-pitched, oscillating noise when the refrigerators are running. Suppose that 7 of these refrigerators have a defective compressor and the other 4 have less serious problems. If the refrigerators are examined in random order, let X be the number among the first 6 examined that have a defective compressor.

Answer 1

The correct answer is 1,51%

Explanation:

To get the probability equally likely of the first 6 examined that have a defective compressor, we use the following formula

P=# of possibilities that meet the condition / #of equally likely possibilities.

As there are multiple events , and all must be achieve, we multiply the probabilities.

P1=7 / 11

P2=6 / 10

P3=5 / 9

P4=4 / 8

P5=3 / 7

P6=2 / 6

P(x)=7 / 11*6 / 10*5 / 9*4 / 8*3 / 7*2 / 6=0,01515151515

P(x)=1,51%