of the five - digit positive integers that have no digits equal to zero , how many have two digits that are equal to each other and the remaining digit different from the other two ?
"of the five - digit positive integers that have no digits equal to zero , how many have two digits that are equal to each other and the remaining digit different from the other two ? a . 24 b . 36 c . 72 d . 144 e . 216 choosing the digit for p - 9 ways ; choosing the digit for q - 8 ways ; choosing the digit for r - 7 ways ; choosing the digit for s - 6 ways ; # of permutations of 3 digits in ppqrs - 5 ! / 2 ! total : 9 * 8 * 7 * 6 * 5 ! / 2 ! = 181440 . answer : d ."
multiply(multiply(subtract(const_10, const_1), subtract(const_10, const_2)), const_1)