in a box of 10 pens , a total of 3 are defective . if a customer buys 2 pens selected at random from the box , what is the probability that neither pen will be defective ?
"# defective pens = 3 # good pens = 7 probability of the 1 st pen being good = 7 / 10 probability of the 2 nd pen being good = 6 / 9 total probability = 7 / 10 * 6 / 9 = 7 / 15 the answer is c ."
multiply(divide(subtract(10, 3), 10), divide(subtract(subtract(10, 3), const_1), subtract(10, const_1)))