Question

The tables below show running hours of three printers that produce greeting cards and the total number of greeting cards produced over three weeks.

Number of Hours Machine Is Running

Printer A
Printer B
Printer C
Week 1
40
50
45
Week 2
45
50
35
Week 3
50
40
50


Total Cards Produced
Week 1
7,950
Week 2
7,350
Week 3
8,700

Printer B uses $15 in ink every hour. What is the ink cost for each card coming from printer B?

Answer 1

Let a, b, c be cards per hour for printers A, B, C. From the three weeks:

40a + 50b + 45c = 7950
45a + 50b + 35c = 7350
50a + 40b + 50c = 8700

Subtracting week2 from week1: -5a + 10c = 600 → a = 2c - 120.
Using this in week1 and simplifying gives c = 90, so a = 60 and b = 30 cards/hour.

Printer B uses $15 per hour, so ink cost per card = 15 / 30 = $0.50 (50 cents) per card.