Question

A plane is missing and it is presumed that it was equally likely to have gone down in any of the 3 possible regions. If the plane is in region 1, it will be found with probability 0.70. If the plane is in region 2, it will be found with probability 0.40. And, if the plane is in region 3, it will be found with probability 0.30. What is the probability that during a search, the plane is not found in region 1?

Answer 1

It is easier to create a probability table.

FOUND NOT FOUND TOTAL
REGION 1 0.70 0.30 1
REGION 2 0.40 0.60 1
REGION 3 0.30 0.70 1

The probability that during the search, the plane is not found in region 1 is 0.30. (1 - 0.70)