Question

A box contains 20slips numbered from 1 to 20 and another box contains 30 slips numbered from 1 to 30.One slip is taken from each box. In how many different ways we can select a pair of slips one from each box. What is the probability of both being even. What is the probability of getting an even number and an odd number. What is the probability of getting at least an even number.

Answer 1

There are 20x30= 600 different ways to select a pair of slips one from each box.

There are 10 even slips in the first box and the probability of selecting an even slip is 1/2.

There are 15 even slips in the second box and the probability of selecting an even slip is 1/2.

So the probability of of selecting two even slips is 1/2 x 1/2 = 1/4.

But the probability of selecting an odd slip from either box is also 1/2.

So the probability of selecting an even slip and an odd slip is 1/2 x 1/2 = 1/4.

The probability of selecting at least an even number slip is just 1/2.  

That is the probability of getting an even slip from one box, and it doesn't matter what the slip from the other box will be.