Question

A shipment of 10 computers contains 2 with defects. Find the probability that a sample of size 2​, drawn from the ​10, will not contain a defective computer.

Answer 1

`(28)/(45) .`

Explanation:

way_1:

according to the condition the probability for the 1st computer is 8/10=4/5;

for the 2d computer is 7/9. Then the final probability is P=4/5 * 7/9=28/45;

way_2:

the required probability can be calculated according the formula:

`P=(no-cases)/(total-cases);`

then

`P=(C^2_8)/(C^2_(10)) =(2!8!8!)/(2!6!10!)=(28)/(45) .`