The time (in minutes) between telephone calls at an insurance claims office has the exponential probability distribution:

The time (in minutes) between telephone calls at an insurance claims office has the exponential probability distribution

f (x) = 0.50 e-0.50x for x ≥ 0.

what is probability of 30 seconds or less between phone calls.

If this is the complete question.

First, convert 30 seconds to. 5 minutes. The mean time between phonecall is u=2.

P (x is less than. 5) 1-e^5/2 = 0.2212

So the answer was approximately 22%.