there are 10 slate rocks , 11 pumice rocks , and 4 granite rocks randomly distributed in a certain field . if 2 rocks are chosen at random and without replacement , what is the probability that both rocks will be slate rocks ?
"10 / 25 * 9 / 24 = 3 / 20 the answer is a ."
multiply(divide(10, add(add(10, 11), 4)), divide(subtract(10, const_1), subtract(add(add(10, 11), 4), const_1)))