Question

A company called Blurb prints books. According to its advertisement, you get a 15% discount on all orders of 51 or more copies of the same book (up to 100 copies). Is the cost per order a linear function of the number of copies you order (up to 100)?

Answer 1

Yes, the cost per order is a linear function of the number of copies you order (up to 100).

Explanation:

Let;

y = Total cost of order from one copy up to 100 copies or dependent variable

a = Cost of 50 copies or fixed intercept

x = Cost of 51 copies or more up to 100 copies or dependent variable, i.e. 51 = x
`\leq` 100

b = Coefficient of x = 1 - Discount rate = 1 - 15% = 1 - 0.15 = 0.85

We can therefore represent have a function as follows:

y = a + bx ........................ (1)

Substituting b = 0.85 into equation (1), we have:

y = a + 0.85x ...................... (2)

Equation (2) implies that as b equal to 51 or more up to 100, y also increases. Equation (2) is therefore an example of linear function which will give an upward sloping straight line and can be rewritten as:

y = f(x) = a + 0.85x ................. (3)

Therefore, the cost per order is a linear function of the number of copies you order (up to 100).