The average retail price of gasoline for 2014 was 342 cents. What would the standard deviation have to be in order for there to be a 15% probability that a gallon of gas costs less than $3.00?

40.38 cents.

Step-by-step explanation:

In this case, the following formula must be applied:

z = (x-mean) / sd

sd is the standard deviation

If we reorganize, we are left with:

sd = (x-mean) / z

We know that 100 cents is 1 dollar, therefore 342 cents are $ 3.42, that is the value of the average. The value of "x" would be the one we want to compare with, it is $ 3.

z, we must look for it in the normal distribution table, we must look inside the table for the value of 0.15 (15%), which is the closest value, and they would be 0.1492, which corresponds to a value of z of -1.04.

Replacing all the values we are left with:

sd = (3.00-3.42) / - 1.04

sd = 0.4038

Therefore the standard deviation would be $ 0.4038 dollars or 40.38 cents.

the speed is   miles per hour > is false

step-by-step explanation:

we know that  

a relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form or

in a proportional relationship the constant of proportionality k is equal to the slope m of the line and the line passes through the origin

the graph shown in the figure represent a direct variation

the slope of the line represent the speed

for the point

substitute the values of x and y

the linear equation is equal to

statements

case a) it takes hours to go miles

the statement is true

because

substitute

for

find the value of y in the linear equation

> is correct

case b) the speed is   miles per hour

the statement is false

because the speed is

case c) the unit rate for the trip is

the statement is true

because the speed is equal to the slope of the linear equation

case d) it took minutes to go the first miles

the statement is true

because

substitute

for

find the value of y in the linear equation

> is correct