Question

NEED ASAP!!!!!

The graph shows a school's profit for selling lunches
on pizza day. What is the cost for selling 100
lunches? You must show your work.

Answer 1

The cost for selling 100 lunches is 150 dollars.

Explanation:

First, consider the equation: y = mx + b
y in this case is the profit in dollars (what' on the y axis) x in this case is the number of lunches sold (x- axis), m is the slope.

How do we calculate the slope of a graph? we take two points from the graph, let's say, (65,45) and (20,-90)

the formula for finding the slope is:

`(rise)/(run) = (y2 - y1)/(x2-x1) \\\\`

where (x1, y1) is coordinates of first point in the line

where (x2, y2) is coordinates of second point in the line

`(45-(-90))/(65-20) = 3`

m = 3

y = 3x + b

now we need to find b. We just insert one point of your choice from the grpah, let's choose (50,0) now plug them in out newfound equation (y = 3x + b)

0 = 3(50) + b

find b using algebra:

0 = 150 + b

b = -150

Yay! we found b, now we have the equation y = 3x - 150

(by the way I just noticed you can find b from the graph, the point that touches the y-axis is b)

now we are told to find the cost for selling 100, we need to plug in 100 instead of x in our equation.

y = 3(100) - 150 = 150

therefore the cost is 150 dollars.

hope this helps, tell me if you misunderstood something.