Question

BatCo, a company that sells batteries, claims that 67.5% of their batteries are in working order. How many batteries would you expect to buy, on average, to find one that does not work.

Help!

Answer 1

okay that was wrong sorry
if \(67.5\%\) work, then \(32.5\%\) do not
i.e. the probability that one does not work is \(0.325\)
the expected number to buy therefore is the reciprocal of \(0.325\) whatever that is

Answer 2

This question seem to be missing some data, cause even though the percentage of batteries that won't work is known, there isn't any actual number of batteries I can use the percentage on. Sigh.. Maybe I should write the reviews.

Answer 3

no it is not missing information
the expected waiting time is the reciprocal of the probability

Answer 4

if one out of every 100 batteries are defective, then you expect to have to test 100 before you find a defective one

Answer 5

if the probability that a battery is defective is \(0.325\) then you expect to have to test
\[\frac{1}{.325}=3.0769...\] before you get a defective one

Answer 6

assuming independence, which you are in this case

Answer 7

thank you, for the help. Now I understand xD