Question

The average speed of a car driving down freeway is 70mph with a standard deviation of 5mph. Thid speed is normally distributed. Find the following.A) what is the probability that a randomly selected car is driving more than 77mph?B) what is probability that a randomly selected car is driving between 65 and 69 mph?C) what is the probability that a randonly selected car is driving between 67 and 77mph?D) what is the probability that a randomly selected car is driving less than 77mph?

Answer 1

Answer:

0.081,0.2621,0.645,0.919

Step-by-step explanation:

Let X be the average speed of a car driving down freeway

Given that X is normal with mean as 70mph with a standard deviation of 5mph.

To convert to Z score we do

$Z =\frac{x-70}{5}$

a)  the probability that a randomly selected car is driving more than 77mph

$=P(X>77)\\=P(Z>1.4)\\=0.081$

b) probability that a randomly selected car is driving between 65 and 69 mph

= $P(-1$

c) the probability that a randonly selected car is driving between 67 and 77mph

=$P(-0.6$

d) the probability that a randomly selected car is driving less than 77mph

$=P(Z$