how many 4 digit odd numbers do not use any digit more than once
the way i solved it is a b c d ( thousand , hundreds , tens , units ) d can be 1 3 5 7 9 ( any of the 5 digits ) a can be anything except ( d or 0 ) so 8 possibilities c can be anything execpt a and b so 8 possibilities b can be anything execpt ( a d c ) so 7 possibilities total ways are 8 * 7 * 8 * 5 = 2240 ans e
multiply(multiply(multiply(add(4, const_1), subtract(subtract(const_10, const_1), const_1)), subtract(subtract(const_10, const_1), const_1)), subtract(subtract(subtract(const_10, const_1), const_1), const_1))