I believe this problem has the following table for long distance call:
0-1 minutes 2-5 minutes 6+ minutes
Long distance 170 120 10
To solve this problem, let us first recall what probability means:
Probability = number of successful event / number of total events
In this case, an event is considered to be successful when the long distance call is not 6+ minutes long. Therefore:
number of successful event = 170 + 120 = 290
Now the number of total events is the sum of all number of calls, hence,
number of total events = 170 + 120 + 10
number of total events = 300
Probability that the call is not 6+ minutes long is therefore:
Probability = 290 / 300
Probability = 0.9667
or
Probability = 96.67%
