Question

Daniel is printing out copies of a presentation. It takes 3 minutes to print a color copy and 1 minute to print a black-and-white copy. He needs to print at least 6 copies and must have the copies completed in no more than 12 minutes.
If the solution region represents the number of color copies and black-and-white copies that Daniel can print, determine which graph represents the solution set to the system of inequalities representing this situation.

Answer 1

Work the information to set inequalities that represent each condition or restriction.

2) Name the variables. 

c: number of color copies
b: number of black-and-white copies

3) Model each restriction:

i) It takes 3 minutes to print a color copy and 1 minute to print a black-and-white copy.

3c + b


ii) He needs to print at least 6 copies ⇒ c + b ≥ 6


iv) And must have the copies completed in no more than 12 minutes ⇒

3c + b ≤ 12


4) Additional restrictions are c ≥ 0, and b ≥ 0 (i.e. only positive values for the number of each kind of copies are acceptable)

5) This is how you graph that:

i) 3c + b ≤ 12: draw the line 3c + b = 12 and shade the region up and to the right of the line.

ii) c + b ≥ 6: draw the line c + b = 6 and shade the region down and to the left of the line.

iii) since c ≥ 0 and b ≥ 0, the region is in the first quadrant.

iv) The final region is the intersection of the above mentioned shaded regions.

v) You can see such graph in the attached figure.