Answer:

Step-by-step explanation:
The nth term of a geometric sequence is given by the following equation.

In which r is the common ratio.
This can be expanded for the nth term in the following way:

In which
is the first term.
This means that for example:

So




Then

Answer:
Expected number of hours before the the group exits the building = E[Number of hours] = 3.2 hours
Step-by-step explanation:
Expected value, E(X) is given as
E(X) = Σ xᵢpᵢ
xᵢ = each variable
pᵢ = probability of each variable
Let X represent the number of hours before exiting the building taking each door. Note that D = Door
D | X | P(X)
1 | 3.0 | 0.2
2 | 3.5 | 0.1
3 | 5.0 | 0.2
4 | 2.5 | 0.5
E(X) = (3×0.2) + (3.5×0.1) + (5×0.2) + (2.5×0.5) = 3.2 hours
Hope this Helps!!!
I think the answer would be C. (btw, you should charge your phone/tablet, lol)