9 . E
To find the probability, you need to know the number of favorable
outcomes and the total number of possible outcomes. The latter is the
number of combinations of 10 items taken 2 at a time:
To find the number of favorable outcomes, it’s easiest to find the number
of unfavorable outcomes (that is, where the numbers add up to 6 or less)
by listing and counting them. These are the only unfavorable
combinations:
All the other 45 − 6 = 39 outcomes are favorable, and the probability is 39
÷ 45 = 0.87.
