# math contest problem on probability.

• Nov 11th 2009, 10:04 PM
Vicky1997
math contest problem on probability.
Two fair coins are to be tossed once. For each head that results, one fair die is to be rolled. What is the probability that the sum of the die rolls is odd? ( Note that if no die is rolled the sum is 0)

I could think of the cases

HH the sum to be odd is 18/36
HT one die rolled 3/6 is odd
TH one die rolled 3/6 is odd
TT

I'm stuck from here....

Vicky.

My knowledge of probability is very basic so could this please be explained as easy as possible?
• Nov 12th 2009, 03:00 AM
mr fantastic
Quote:

Originally Posted by Vicky1997
Two fair coins are to be tossed once. For each head that results, one fair die is to be rolled. What is the probability that the sum of the die rolls is odd? ( Note that if no die is rolled the sum is 0)

I could think of the cases

HH the sum to be odd is 18/36
HT one die rolled 3/6 is odd
TH one die rolled 3/6 is odd
TT

I'm stuck from here....

Vicky.

My knowledge of probability is very basic so could this please be explained as easy as possible?

Pr(HH) = 1/4, Pr(HT) = 1/4 .....

So the answer will be (1/4)(18/36) + (1/4)(3/6) + .... = ....
• Nov 12th 2009, 07:25 PM
Vicky1997
Quote:

Originally Posted by mr fantastic
Pr(HH) = 1/4, Pr(HT) = 1/4 .....

So the answer will be (1/4)(18/36) + (1/4)(3/6) + .... = ....

Then it would be 1/8 + 1/8 + 1/8 = 3/8

Thank you!!