in a box of 6 pencils , a total of 2 are defective . if a customer buys 3 pencils selected at random from the box , what is the probability that neither pencils will be defective ?
"first , there are 4 c 3 ways you can select 3 good pencils from 4 good ones . second , there are 6 c 3 ways you select 3 pencils from 6 ones in the box . then , the probability that neither pen will be defective is : 4 c 3 / 6 c 3 = 4 / 20 = 1 / 5 answer is b"
divide(divide(factorial(subtract(6, 2)), multiply(factorial(subtract(subtract(6, 2), 3)), factorial(3))), divide(factorial(6), multiply(factorial(subtract(6, 3)), factorial(3))))