how many different three digit odd numbers without repetitio

Solution

how many different three digit odd numbers without repetitions can be constructed using the digits 2,4,5,7,8 ?

There are 5 digits to choose from and 3 distinct digits must be chosen.

odd numbers end with 5 or 7

Consider the number ends with 5, first two digits are 4*3 =12 possibilities

Consider the number ends with 7, first two digits are 4*3 =12 possibilities

So answer is 12+12 =24 ways.