Help -Joshua, who works for starts every time motors , must put 645 motors through a durability test. Only 3 of the first 45 motors have failed. Using this information , what is the best prediction of the total number of motors that will fail?

Question

Help ->Joshua, who works for starts every time motors , must put 645 motors through a durability test. Only 3 of the first 45 motors have failed. Using this information , what is the best prediction of the total number of motors that will fail?

anonymous · Answer

3/45 motors have failed already, that is 1 in 15 motors have failed.
To make this slightly more understandable, put the motors into groups of 15: there are 43 groups.
Since 1 in 15 motors should fail, each group will have one failing motor giving a total of 43*1 = 43 failures.