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?

Answer: 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

Given:

Today:

Number of printers = 6

Work duration = 12 hours

Tomorrow:

Work duration = 8 hours

At the same rate of printing,

If 6 printer were used to print newspapers for 12 hours.

Only 1 printer will work for 12 * 6 hours at the same rate

But is the printers were 8, (12 * 6) / 8

= 9 printers.

Initial number of printers = 6 printers

Additional printers to be purchased = 9 - 6

= 3 printers