The Bin With The Golf Balls

Imagine a large empty bin where each minute people would come and put in one golf ball a piece.

The first minute (starting at 12 noon), 1 person came and put in a ball.

The second minute, 2 people put in one ball a piece. A minute later, 4 people put in 1 ball a piece.

This pattern continued until the bin was exactly full at 6 PM.

At what time was the bin half empty?