Question

United Express, a nationwide package delivery service, charges a base price for overnight delivery of packages weighing 1 pound or less and a surcharge for each additional pound (or fraction thereof). A customer is billed $ 25 $25 for shipping a 7 7-pound package and $ 55 $55 for shipping a 22 22-pound package. Find the base price and the surcharge for each additional pound. Round answers to the nearest thousandth (to three decimal places).

Answer 1

Base price: $13.

Surcharge: $2 per additional pound.

Explanation:

The base price can be considered a constant, while the surcharge is a function of the additional weight of the package, over 1 pound.

Then, we can model this as a linear function, with additional weight as the independent variable.

`f(x)=b+sx`

being b: base price, and s: surcharge for each additional pound.

The 7-pound package cost $25. The additional weigth in this case is 7-1=6 pounds.

The 22-pound package cost $55. The additional weigth is 21 pounds.

So we have the first point (6, 25):

`f(6)=b+s(6)=25\\\\b=25-6s`

Then, for the second point (21, 55) we have:

`b=25-6s\\\\f(21)=(25-6s)+s(21)=55\\\\25+(21-6)s=55\\\\15s=55-25=30\\\\s=30/15=2\\\\\\b=25-6(2)=25-12=13`

Then, the prices are:

Base price: $13.

Surcharge: $2 per additional pound.