Question

a pair of dice is rolled. find the probability that at least one of them is greater than or equal to 4

can any one please help me with this. Its driving me nuts !! hae exam tomorrow
thanks in advance

Answer 1

The sample space has 36 possible combinations of numbers. These can be set out in column form as follows:
6,6 5,6 4,6 3,6 2,6 1,6
6,5 5,5 4,5 3,5 2,5 1,5
6,4 5,4 4,4 3,4 2,4 1,4
6,3 5,3 4,3 3,3 2,3 1,3
6,2 5,2 4,2 3,2 2,2 1,2
6,1 5,1 4,1 3,1 2,1 1,1
You need to count up the number of outcomes where at least one of dice reads greater than or equal to 4. Then divide that number of outcomes by 36 to find the required probability.

Answer 2

wow! i was wondering what was taking so long
nice table!

Answer 3

i was going to say find the pairs where both are less than 4
the 9 pairs in the bottom right of the table, but the table is best, especially for an exam

Answer 4

Thanks. When I made it the first time I saved it for future use.

Answer 5

@kropot72 and @satellite73 thank u both of u for answering
so table is the only way? u make the table and find the where it is greater than equal to 4
I was counting the possibilities of greater than or equal to 4 but I thought that i am doing something really wrong !! but i was right
thanks for the help !

Answer 6

You're welcome. The table is the surest way.

Answer 7

what if it says atleast one of them is >= 4, given that the sum is >=8 ?

Answer 8

is it the same way as saying the sum is >=8 given that atleast one of them is >=4

Answer 9

If the sum of the two numbers is equal to or greater than 8, then at least one of the numbers must be equal to or greater than 4 in every case.
Therefore, given that the sum of the numbers is equal to or greater than 8, the probability that at least one of the numbers is equal to or greater than 4 is 1.