Problem:
Math Club members want to advertise their fundraiser each week in the school paper. They know that a front-page ad is more effective than an ad inside the paper. They have a $30 advertising budget. It cost $2 for each front-page ad and $1 for each inside page ad. The club wants to advertise at least 20 times.
a) Write and graph a system of inequalities to model the number of advertisements the club can purchase to stay under budget. Be sure to label all parts of your graph.
Solution:
Let us denote the number of front-page ads by x, and the number of inside ads by y:
x = number front-page ads
y= number of inside ads
Now, because they have a $30 advertising budget and It cost $2 for each front-page ad and $1 for each inside page ad, the first inequality that we have is:
If we represent the graph of the equality (line) 2x+y = 30, we have:
On the other hand, because the club wants to advertise at least 20 times, the second inequality that we have is:
If we represent the graph of the equality (line) x+y = 20, we have:
Now, the intersection point of the above lines, that is 2x+y = 30 and x+y = 20 is found as follows:
we have
y = 30 - 2x
and
y = 20-x
then
30-2x = 20-x
and
30-20 = 2x-x
that is
10 = x
when x = 10 then y = 20-x = 20-10 = 10