Posted by **is this right!!!** on Tuesday, June 16, 2009 at 11:03am.

A die is rolled once. What are the odds against rolling a prime number? 2

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**Reiny**, Tuesday, June 16, 2009 at 11:11am
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 = 1-1/2 = 1/2

so the odds in favour of a non-prime = (1/2) ÷ (1/2)

= 1:1

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**John**, Tuesday, June 16, 2009 at 11:16am
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

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**Reiny**, Tuesday, June 16, 2009 at 11:21am
Euler considered 2 to be the first prime, and who are we to argue against Euler.

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**hannah**, Saturday, March 26, 2011 at 8:10pm
yes

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