7,8 |

48 blacksmiths need to shoe 60 horses. What is the minimum time they will spend on the work if each blacksmith spends 5 minutes on one horseshoe

#
Notice that four blacksmiths cannot shoe one horse at the same time.

## Solution

It will take no less than $60 \cdot 4 \cdot 5: 48=25$ minutes. For this, it is necessary that none of the blacksmiths are idle. It is sufficient to show that four blacksmiths can shoe five horses in 25 minutes. For this, arrange the five horses in a circle. Four blacksmiths approach the first four horses and shoe (in 5 minutes) one hoof each. Then each moves to the next horse clockwise and so on.