There are six printers at "Today's news" newspaper, each printing at the same constant rate. Working together, the six printers can complete printing tomorrow's newspaper within 12 hours. If the owner wishes to reduce the printing time to 8 hours, how many additional printers, each with the same constant rate, will he need to purchase?

3

Explanation:

Printers are said to be working at a constant rate with 6 printers working for 12 hours. This means in other to achieve a similar output with 1 printer;

12 hours × 6 = 72 hours

Total hours required to complete printing = 72 hours

Assuming adding more printers working at constant rate in other to reduce completion hours to 8

Total completion hours ÷ number of printers = 8 hours

72 ÷ number of printers = 8

Nunber of printers = 9

Therefore, number of printers that must be added = 9 - 6 = 3