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Question
A bag contains 50 coins and each coin is marked from 51 to 100. One coin is picked at random. The probability that the number on the coin is not a prime number, is
Options
`1/5`
`3/5`
`2/5`
`4/5`
Solution
The total number of trials is 50.
Let A be the event that the number on the picked coin is not a prime.
The prime’s lies in between 51 and 100 are 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97. They are 10 in numbers. Therefore the numbers lies between 51 and 100 and which are not primes are 50-10=40 in numbers.
So, the number of times A happens is 40.
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) = 40/50 `
`= 4/5`
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