Answer
2/5
Work Step by Step
P(event)=$\frac{numberoffavorableoutcomes}{numberofpossibleoutcomes}$
There are 20 differences between the stem and leaf plot so this is the number of possible outcomes. Out of the 20, eight are less than 10 points:1, 3, 3, 3, 3,4, 7, 7 so this is the number of favorable outcomes.
So, the probability is:
P(less than 10 points)=$\frac{8}{20}$ -simplify-
P(less than 10 points)=$\frac{2}{5}$
