Question

State sales tax y is directly proportional to retail price x. An item that sells for 156 dollars has a sales tax of 14.42 dollars. Find a mathematical model that gives the amount of sales tax y in terms of the retail price x .

What is the sales tax on a 320 dollars purchase.

Answer 1

The sales tax on a 320 dollars purchase is of $29.6.

Explanation:

State sales tax y is directly proportional to retail price x.

This means that:

`y = cx`

In which c is the constant of proportionality.

An item that sells for 156 dollars has a sales tax of 14.42 dollars.

This means that
`x = 156, y = 14.42`. We use this to find c. So

`y = cx`

`14.42 = 156c`

`c = (14.42)/(156)`

`c = 0.0924`

Then

`y = 0.0924x`

What is the sales tax on a 320 dollars purchase?

y when
`x = 320`. So

`y = 0.0924(320) = 29.6`

The sales tax on a 320 dollars purchase is of $29.6.