The answer is B. In this case when you isolate the variable it just takes 2 steps. The others require more steps and tedious calculation.
The entire system forms a right angle triangle.
Let the height of the bulding be x, then tan 45 = (x - 6)/60
60 = x - 6
x = 60 + 6 = 66
Therefore the height of the building is 66 feet.
We need to find the probability of atleast one failure in 5 trails
Probability of success = 30% = 3/10
The opposite meaning of atleast one failure is all success (no failures)
Probability of (atleast one failure ) = 1- Probability ( success)
First we find probability of success
Formula for binomial distribution
All success so n=5, r=5, p= 3/10, q= 1-p = 7/10
Probability (success) =
=
Probability (atleat one failure) = 1 -
= 0.92224
= 92.2%
The answer is 36 i use foil and cheaked in calculator