Dave and mary depart from the bus station at 10 am traveling in opposite directions. dave's bus is going 40 miles per hour and mary's is going 50 miles per hour. at what time will they be 270 miles apart?

  In 3 hours they will be 270 miles apart.

Since Dave and Mary are going opposite directions every hour mary will be moving 50 miles away and Dave will be moving 40 miles away meaning they will move 90 miles away from each other every hour. So 270 is 90 times three so in three hours they will be 270 miles away so at 1 pm they will be 270 miles apart.

Agreed i also had the same answer