Question

Joanne bought 3 pens and and 2 rulers for $10.80. Alice bought 5 pens and 4 rulers for $19.20. Nick bought 2 rulers and some pens. If Nick spent $13.20, how many pens did Nick buy?

Answer 1

Answer:

4

Step-by-step explanation:

• Pen = p and ruler = r
• 3p + 2r = 10.8
• 5p + 4r= 19.2
• get the r to cancel out
• 5p + 4r= 19.2
• -6p - 4r = -21.6
• -p = -2.4
• p = $2.40
• now solve for r by substituting p back into the equation
• 3p + 2r = 10.8
• 3(2.4) + 2r = 10.8
• 7.2 + 2r = 10.8
• 2r = 3.6
• r = $1.80
• Now that we know the cost per pen and per ruler we can find out how many pens Nick bought
• 2(1.8) = 3.6
• 13.2 - 3.6 = $9.60 (the amount spent on pens)
• $9.60/$2.40 = 4
• Nick bought 4 pens