Posted by is this right!!! on .
A die is rolled once. What are the odds against rolling a prime number? 2

math 
Reiny,
odds in favour of some event
= prob(of that event/prob(not that event)
primes form 1 to 6 are 2,3, and 5
so prob of a prime = 3/6 = 1/2
so prob of not a prime = 11/2 = 1/2
so the odds in favour of a nonprime = (1/2) รท (1/2)
= 1:1 
math 
John,
first off, what are the prime numbers?
a prime number is any number divisible by one and itself.
1, 2, 3, 5, are all prime numbers.
although 1 can be controversial. Some teachers consider 1 as a prime but some not. anyways assuming 1 is a prime. there is a total of 4 primes.
a dice has six sides of six numbers total.
so the probablility of rolling a prime number is:
4/6 and if you simplify: 2/3
but if you don't consider 1 as a prime:
the answer would be: 3/6 and simplify: 1/2 
math 
Reiny,
Euler considered 2 to be the first prime, and who are we to argue against Euler.

math 
hannah,
yes