Word problem

Question

Troy and Lisa were shopping for school supplies. Each purchased different quantities of the same notebook and thumb drive. Troy bought 5 notebooks and 5 thumb drives for $75. Lisa bought 2 notebooks and 6 thumb drives for $78. Find the cost of each notebook and thumb drive.

Answer 1

Sarah,

Let x = cost of notebook

let y = cost of thumbdrive

 

For Troy   5x + 5y = 75

For Lisa    2x + 6y = 78

 

I want to use elimination, but nothing looks pretty.  Let's play with Troy's equation.  Let's divide it by 5 and get 

x+ y = 15     multiply by -2

-2x -2y  = -30

2x + 6y = 78    Add equations

       4y = 48

Solve for y.  Then plug it in one of the original equations and solve for x.  Check by plugging into the other original equations.

Voila!

Mary