Gold Thief

Puzzle number 20.

A girl has stolen two bars of solid gold, each weighing 20 pounds, and is running from some police. On the path she is on, she comes up to a rope bridge with a sign saying that the rope bridge can hold a maximum weight of 130 pounds, and that if any more weight is placed on the bridge it will collapse.

The girl knows her weight is 100 pounds, so she walks across the bridge carrying both gold bars, and the bridge does not break. How is this possible?