Answer:
a)
And we can find this probabiliy using the normal standard table or excel and we got:
So then we expect about 4%
b)
And we can find this probabiliy using the complement rule and the normal standard table or excel and we got:
So then we expect about 8.5%
Step-by-step explanation:
Part a
Let X the random variable that represent the speeds of vehicles, and for this case we know the distribution for X is given by:
Where and
We want to find this probability (legal speed)
We can use the z score given by:
If we apply this formula to our probability we got this:
And we can find this probabiliy using the normal standard table or excel and we got:
So then we expect about 4%
Part b
And we can find this probabiliy using the complement rule and the normal standard table or excel and we got:
So then we expect about 8.50%