# Math forum

 Probability Options
rallycat19
 #1 Posted : Friday, November 11, 2011 6:36:37 PM
Rank: Newbie

Groups: Registered Users

Joined: 11/11/2011
Posts: 1

The faces of a fair cube are numbered 1 through 6, the probability of rolling any number from 1 through 6 is equally likely. If the cube is rolled twice, what is the probability that an even number will appear on the top face in the first roll or that the number 1 will appear on the top face in the second roll?

Thank you!

 #2 Posted : Sunday, December 04, 2011 11:51:13 AM
Rank: Member

Groups: Registered Users

Joined: 3/21/2011
Posts: 20

rallycat19 wrote:

The faces of a fair cube are numbered 1 through 6, the probability of rolling any number from 1 through 6 is equally likely. If the cube is rolled twice, what is the probability that an even number will appear on the top face in the first roll or that the number 1 will appear on the top face in the second roll?

Thank you!

hi

the sample space for this is {1,2,3,4,5,6}

Given that on the first roll, an even no. appears.

so, no. of possible outcomes are 3

Probability of appearance of an even no. on first roll = 3/6 = 1/2

we know that probability of appearance of 1 on top face is 1/6

now, probability of appearance of 1 on top face on 2nd roll is

Probability of appearance of an even no. on first roll * probability of appearance of 1 on top face = (1/2) * (1/6) = 1/12

hope i'm not wrong!!

itsmyflow
 #3 Posted : Thursday, December 15, 2011 9:35:52 PM
Rank: Newbie

Groups: Registered Users

Joined: 12/15/2011
Posts: 3

rallycat19 wrote:

The faces of a fair cube are numbered 1 through 6, the probability of rolling any number from 1 through 6 is equally likely. If the cube is rolled twice, what is the probability that an even number will appear on the top face in the first roll or that the number 1 will appear on the top face in the second roll?

Thank you!

on the first roll there is a possible of 3 even numbers on a dice from 1-6. -> 3/6 =1/2

on the second roll the chance of rolling a 1 is 1/6 chance.

the probability that an even number or the number 1 will appear on the top face on the second roll is->

1/2 + 1/6= 7/12

In an "or" problem you add the probability

In an "and" problem you multiply the probability

Users browsing this topic
Guest
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

YAFPro Theme Created by Jaben Cargman (Tiny Gecko)