8.7k views
4 votes
4. Jon orders 4 shirts for $35. Later he orders 12 shirts for $95. Because he is anew customer, the shipping cost is a reduced value for his first five orders.Predict the cost of 10 shirts on his third order.

1 Answer

4 votes

we are given the cost for 4 shirt s and for 12 shirts. Assuming that the shipping cost is constant, we can model the cost of the shirts as a linear equation. So, we want to find an equation of the form


y=mx+b

where m is the slope of the line and b is the y-intercept.

Using the given information, we can wirte the following points (4,35) and (12,95). We will use this points to find the value of b and m.

Recall that the slopé of a line that passes through points (a,b) and (c,d) is described by the formula


m=\frac{d\text{ -b}}{c\text{ -a}}=\frac{b\text{ -d}}{a\text{ -c}}

in our case, we have a=4, b=35, c=12 and d=95. So we get


m=\frac{95\text{ -35}}{12\text{ -4}}=(60)/(8)=(30)/(4)=(15)/(2)=7.5

So, so far we have the equation


y=7.5x+b

To find the value of b, we will use tghe fact that, as the line should pass through the point (4,35), this means that if we replace x by 4, we should replace y by 35. So we have that


35=7.5\cdot4+b=30+b

so if we subtract 30 on both sides, we get


b=35\text{ -30=5}

so the line equation would be


y=7.5x+5

Now, we want to find the price for 10 tshirts. So we simply replace x=10 to find


y=7.5\cdot10+5=75+5=80

so the price of 10 tshirts is 80

User BPCorp
by
8.7k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories