This machine had operated for 24 hours a day, five or six days a week, since 1987.

The surgeon has been operating for four hours; he's hungry.

As a test, they operated one of her boilers for 36 hours without any problems.

It operates for up to 10 hours and has a dimmer.

First, the doctor stopped the considerable bleeding; then, he operated for more than two hours.

The company employed approximately 325 people and operated six days a week for ten hours a day.

They were generally operated for only a few hours at a time, usually during peak power consumption in the afternoon.

We do not have enough electrical power even to operate our environmental control systems for more than a few hours.

It operates for about 8 hours in a day.

Currency exchanges may operate for only three and a half hours a day instead of seven.