Question

You want to deliver a package to Japan. The FedEx delivery service charges a $15 flat fee plus $2 per additional kilogram. You can also use the USPS Priority Mail service which charges you $5 per kilogram. After how many kilograms will the total costs of the two options be the same?

Answer 1

5kg

Explanation:

Step 1.

Write in y=mx+c format

m= $/kg

c=flat fee

x=additional kilograms

FedEx:

y=2x+15

USPS:

y=5x

Step 2.

Keep Changing the x value (the no. of kilograms) in both equations until y is the same number

y=5×5

=25

y=2×5+15

=25

∴It would cost the same for both options at 5kg

Answer 2

5kg

Explanation:

Step 1.

Write in y=mx+c format

m= $/kg

c=flat fee

x=additional kilograms

FedEx:

y=2x+15

USPS:

y=5x

Step 2.

Keep Changing the x value (the no. of kilograms) in both equations until y is the same number

y=5×5

=25

y=2×5+15

=25

∴It would cost the same for both options at 5kg