Question

A die is thrown 100 times. If the probability of getting an even number is `2/5` . How many times an odd number is obtained? 

Answer 1

The total number of trials is 100. Let the number of times an even number is obtained is x.

Let A be the event of getting an even number.

The number of times A happens is x.

Remember the empirical or experimental or observed frequency approach to probability.

If n be the total number of trials of an experiment and A is an event associated to it such that A happens in m-trials. Then the empirical probability of happening of event A is denoted by P (A) and is given by

` P (A) = m/n`

Therefore, we have ` P (A) = x/100` .

But, it is given that ` P (A) = 2/5`. So, we have

`x/100 = 2/5`

⇒ 5x = 200

⇒ `x = 200/5`

⇒ x = 40 

Hence an even number is obtained 40 times. Consequently, an odd number is obtained 100 - 40 = 60 times.