Table of values

Question

Cora is going to ship some gifts to family members, and she is considering two shipping companies. The first shipping company charges a fee of $20 to ship a medium box, plus an additional $2 per kilogram. A second shipping company charges $10 for the same size of box, plus an additional $3 per kilogram. At a certain weight, the two shipping methods will cost the same amount. What is that weight?

Answer 1

Hi Alondra! I promise this is a simple problem!

First, let w=the weight you are looking for. The company charges 2w + 20 and the 2nd company charges 3w + 10. So that will give you this:

2w + 20 = 3w + 10

Subtract 2w from both sides which will leave you with 20 = w + 10. Subtract 10 from both sides and you get 10 = w. The weight that makes the companies charge the same is 10 lbs!

 

Answer 2

First, set up a system of equations. Let X be the weight in kilograms and Y be the total cost. Because the question says at a certain weight, both will cost the same, this infers that both equations will have the same Y, aka the same cost, which allows us to set the equations equal to one another.

20 + 2X = Y

10 + 3X = Y Set Equation equal to one another

20 + 2X = 10 + 3X Solve for X

10 = X

When the two costs are equal, the weight will be 10 kilograms.