# If a number is chosen at random from the following list, what is the probability that it is not prime? 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Asked on by alicesmith

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

We have a list of 10 numbers from 1 to 10 consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Now the prime numbers in this list are 2, 3, 5 and 7. We have to remember that 1 is not a prime number as a prime number is a number that has exactly 2 factors. So the numbers that are not prime are 1, 4, 6, 8, 9 and 10. There are 6 such numbers.

If a number is picked at random from this list the possibility of picking a number that is not prime is 6/10 or 3/5 or 60%.

The required probability is 60%.

neela | High School Teacher | (Level 3) Valedictorian

Posted on

The number of numbers in the list are 10.

The primes are 2, 3,5,7.

So the number of numbers which are prime in the list = 4.

Therefore , probability of an event = number of  ways of happening favourable to the eevent/ Total number of ways = 4/10 = 0.4.

Therefore  the prabability that if a number is chosen at random from the list of numbers: 1,  2,  3,  4 ,   5,   6,  7,   8,   9 and 10, the chose number is prime is 0.4.

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