A train 280 meters long travels at a speed of 18 meters per second across a bridge. It takes 20 seconds from the moment the tail of the train gets on the bridge until the head of the train leaves the bridge. Therefore, the length of the bridge is $\qquad$ meters.
【Analysis and Solution】
Train crossing a bridge.
From the tail of the train getting on the bridge to the head of the train leaving the bridge, the distance the train travels is “bridge length - train length”; the length of this bridge is $18 \times 20 + 280 = 640$ meters.