Answer
$\frac{1}{7}$
Work Step by Step
The sample space in Exercise $6$ is:
[1 and 2, 1 and 3, 1 and 4, 1 and 5, 1 and 6, 1 and 7, 2 and 3, 2 and 4, 2 and 5, 2 and 6, 2 and 7, 3 and 4, 3 and 5, 3 and 6, 3 and 7, 4 and 5, 4 and 6, 4 and 7, 5 and 6, 5 and 7, 6 and 7]
From this, we can see that there are $3$ possible combinations which sum up to 7, [1 and 6], [2 and 5], [3 and 4], out of 21 different possible combinations.
We can use the formula $P=\frac{n}{s}$ to calculate the probability.
$P=\frac{n}{s}$
$P=\frac{3}{21}$
$P=\frac{1}{7}$
