Question 1203659: A pair of fair dice is rolled. What is the probability that the number landing uppermost on the first die is 4 if it is known that the sum of the numbers landing uppermost is 7?
that's what i think.
Found 2 solutions by ikleyn, Theo:
Answer by ikleyn(52803)   (Show Source):
You can put this solution on YOUR website! .
If the sum of outcomes is 7, then the number of such outcomes is 6
(these outcomes are (1,6), 2,5), (3,4), (4,3), (5,2), (6,1)).
Of them, only one outcome is favorable: ((4,3).
It gives the probability P =  . ANSWER
Solved.
Answer by Theo(13342)  (Show Source):
You can put this solution on YOUR website! sum of the numbers landing uppermost is 7.
that can be first die plus second die = 1 + 6, 2 + 5, 3 + 4, 4 + 3, 5 + 2, 6 + 1.
the first number of each pair is from the first die.
the possilbe options for the first die, so that the sum is 7, are therefore 1,2,3,4,5,6.
the probability that the value of the first die being 4 would be 1/6 because only 1 out of the 6 possible options for the first die is 4 if the sum is 7
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