Part a
Remember that the linear equation in slope-intercept form is
y=mx+b
where
m is the slope or unit rate
b is the y-intercept or initial value
In this problem
the equation is of the form
C=m(n)+b
where
m=8.50
b=350
therefore
C=8.50n+350
Part b
A reasonable domain for n (number of cups)
Remember that the number of cups cannot be a negative number
so
the domain is the interval [0, infinite)
but a reasonable domain could be [0, 500]
Find out the range
For n=0 -----> C=350
For n=500 ----> C=8.50(500)+350=2,100 ZAR
the range is the interval [350,2,100]
Part c
calculate the cost
For n=100 cups ----> C=8.50(100)+350=1,200 ZAR
For n=200 cups ----> C=8.50(200)+350=2,050 ZAR
For n=400 cups ---> C=8.50(400)+350=3,750 ZAR
Part d
Average cost
Divide the total cost by the number of cups
For 100 cups ------> 1,200/100=12 ZAR per cup
For 200 cups ----> 2,050/200=10.25 ZAR per cup
For 400 cups ----> 3,750/400=9.38 ZAR per cup
Part e
it is better to order more cups, to reduce the initial ZAR 350 cost.
Part f
In this problem we have the ordered pairs
(200, 2150) and (400, 3750)
Find out the slope m
m=(3750-2150)/(400-200)
m=8 ZAR per cup
Find out the linear equation
C=mn+b
we have
m=8
point (200,2150)
substitute and solve for b
2150=8(200)+b
b=2150-1600
b=550
therefore
The linear equation is
C=8n+550
Part g
A reasonable domain could be [0, 600]
Find out the range
For n=0 ------> C=550
For n=600 ----> C=8(600)+550=5,350
The range is the interval [550,5350]
Part h
The gradient is the same as the slope
so
slope=8
that means ----> the cost of each cup is 8 ZAR
Part i
For n=600
C=8(600)+550=5,350 ZAR
Part j
we have the inequality
8n+550 < 8.50n+350
Solve for x
550-350 < 8.50n-8n
200 < 0.50n
400 < n
Rewrite
n > 400
For orders more than 400 cups is more effective to order from Cupomatic
Verify
For n=401
C=8n+550=8(401)+550=3,758 ZAR
C=8.50n+350=8.5(401)+350=3,758.5 ZAR
the cost is less in CUPOMATIC, is ok
the answer is
For orders more than 400 cups is more effective to order from Cupomatic