Answer
$0.8613$
Work Step by Step
Let's find the z-scores for 65,000 and 80,000 miles:
$z=\frac{X-μ}{σ}=\frac{65000-70000}{4400}=-1.14$
$z=\frac{X-μ}{σ}=\frac{80000-70000}{4400}=2.27$
According to Table V, the area to the left of the standard normal curve for a z-score equal to -1.14 is 0.1271.
According to Table V, the area to the left of the standard normal curve for a z-score equal to 2.27 is 0.9884.
The area of the standard normal curve between the z-scores -1.14 and 2.27 is the difference between the area to the left of the standard normal curve for a z-score equal to 2.27 and the area to the left of the standard normal curve for a z-score equal to -1.14:
$0.9884-0.1271=0.8613$
