Question

6 positive integers are taken at random and multiplied together. What is the probability that the product ends in an odd digit other than 5?

Answer 1

The possible odd integers are :

1, 3, 5, 7, 9

They are five in number.

The product ends with a digit other than 5.

The probability that it will end with a digit other than 5is :

It can either end with :

1 or 3 or 7 or 9

This can be written as :

1/5 + 1/5 + 1/5 + 1/5 = 4/5