It is estimated that the time between arrivals of visitors to a public library is an exponential random variable with expected value of 13 minutes. Find the probability that 30 minutes elapses without any arrivals. Enter your answer as just ea/b, where 
is a reduced fraction.
What will be an ideal response?
e-30/13
Mathematics
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Solve the problem.The roof of a building is in the shape of the hyperbola 
where x and y are in meters. Refer to the figure and determine the height h of the outside walls.
a = b = 4 m
A. 9.1 m B. 83 m C. 63 m D. 67 m
Mathematics
Round to the nearest whole number.69.2
A. 69 B. 60 C. 68 D. 70
Mathematics
The following line graph shows the number of hours needed to prepare for various tests. Use the graph to answer the question.
How many hours were needed to prepare for 
.
A. 2 B. 3 C. 5 D. 4
Mathematics
Perform the operation 
using arithmetic for a 12-hour clock.
?
A. 
B. 
C. 
D. 
E. does not exist
Mathematics