Suppose you roll two dice. How do you find the probability that you'll roll a sum of 7?

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Suppose you roll two dice. How do you find the probability that you'll roll a sum of 7?

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Answer 1 · 2016-12-31T09:34:04

Probability that you'll roll a sum of $7$ is $1/6$

Explanation:

When we roll a dice, we can get numbers $1$ to $6$ on each of the dices and hence possible combinations are as follows (here $(x,y)$ means we get $x$ on first dice and $y$ on second dice.)

$(1,1)$ , $(1,2)$ , $(1,3)$ , $(1,4)$ , $(1,5)$ , $(1,6)$ ,

$(2,1)$ , $(2,2)$ , $(2,3)$ , $(2,4)$ , $(2,5)$ , $(2,6)$ ,
.
.
.
$(6,1)$ , $(6,2)$ , $(6,3)$ , $(6,4)$ , $(6,5)$ , $(6,6)$ .

total $36$ possibilities,

of which only $(1,6)$ , $(2,5)$ , $(3,4)$ , $(4,3)$ , $(5,2)$ and $(6,1)$

i.e. $7$ possibilities, result in a sum of $7$ .

Hence, probability that you'll roll a sum of $7$ is $6/36=1/6$

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Suppose you roll two dice. How do you find the probability that you'll roll a sum of 7?

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