Question

A photo lab usually charges 1.45 per print to make a color print from a color transparency. During a special promotion, the charge is $ 1.10 print if 10 or more prints are made. What is the cost of making 19 color prints from transparencies? and what of the prints is a waste of money and why?

Answer 1

`\large \boxed{\math{\$24.05; < 9}}`

Explanation:

Let n = the number of prints

and C = the total cost.

At the regular price, the formula is

C = 1.45n

During the promotion, you must pay for the first nine prints: 9 × 1.45 = 13.05.

For anything over nine prints (n - 9), you must pay $13.05 plus the promotional cost of $1.10 for each print. The promotional formula is

C = 13.05 + 1.10(n - 9) {n > 9}

1. Calculate the cost of 19 prints

`\begin{array}{rcl}C & = & 13.05 + 1.10(19 - 9)\\ & = & 13.05 + 1.10 * 10\\ & = & 13.05 + 11.00\\ & = &24.05\\\end{array}\\\text{The cost of 19 prints is $\large \boxed{\mathbf{\$24.05}}$}`

2. What number of the prints is a waste of money?

During the promotion, buying fewer than nine prints would be a waste of money, because you would not be taking advantage of the promotional savings.