Answer:
1.967 × 10⁻¹¹
Step-by-step explanation:
This is a conditional probability problem
Probability that a 12 year old leaf blower works for 5 more years = Probabilty that a leaf blower works for 17 years, given that it has worked for 12 years = P(17|12)
P(17|12) = P(17 n 12)/P(12)
P(17 n 12) = P(17)
Exponential random variable is given as
f(x) = λ e^(-λ.x)
λ = rate parameter = 5 years per blower
x = variable whose probability is required = 17
f(17) = 17 e^(-5×17)
f(17) = 17 e⁻⁸⁵ = 2.067 × 10⁻³⁶
f(12) = 12 e^(-5×12)
f(12) = 12 e⁻⁶⁰ = 1.051 × 10⁻²⁵
P(17|12) = (2.067 × 10⁻³⁶)/(1.051 × 10⁻²⁵)
P(17|12) = 1.967 × 10⁻¹¹
