Answer:
a) P(X > 10) = 0.6473
b) P(X > 20) = 0.4190
c) P(X < 30) = 0.7288
d) x = 68.87
Step-by-step explanation:
Exponential distribution:
The exponential probability distribution, with mean m, is described by the following equation:

In which
is the decay parameter.
The probability that x is lower or equal to a is given by:

Which has the following solution:

The probability of finding a value higher than x is:

Mean equal to 23.
This means that 
(a) P(X >10)

So
P(X > 10) = 0.6473
(b) P(X >20)

So
P(X > 20) = 0.4190
(c) P(X <30)

So
P(X < 30) = 0.7288
(d) Find the value of x such that P(X > x) = 0.05
So






Negative 72.75 is your product. It is very simple once you understand it.
Answer:
2 people will take 90 days to complete the same house
Step-by-step explanation:
<u><em>Given:</em></u>
T1 = 30 days
P1 = 6
T2 = x
P2 = 2
This is an inverse proportion because if there are more people, less time will be taken to complete the house and vice versa.
<u><em>So, We'll write it in the order of :</em></u>
=> T1:T2 = P2:P1
=> 30:x = 2:6
<u><em>Writing in fraction form</em></u>
=> 
<em>Cross Multiplying</em>
=> 2x = 180
<em>Dividing both sides by 2</em>
=> <u><em>x = 90 days</em></u>
So, <u><em>2 people will take 90 days to complete the same house</em></u>