Answer:
(a) The probability that their sum is also a prime number is 2/3
(b) The probability that their sum is not a 5 is 2/3
Explanation:
We have the numbers 2,3, and 5,
now, 2 + 3 = 5, prime
2 + 5 = 7 prime,
3 + 5 = 8 not a prime,
So, we have 3 cases,
we either get a 5, a 7, or an 8.
where 5 and 7 are primes.
(a) then, the probability that the sum of 2 numbers from 2,3 and 5 is a prime, is (since the primes are 5 and 7) 2/3
2 out of the 3 numbers we get from summing are primes
(b) their sum is not a 5,
since the numbers are 5, 7, 8, the probability the the sum is not a 5 is 2/3, since 2 of the 3 sums are not 5