The slow train is driving from place A to place B. After driving for 1 hour, it is 40 kilometers away from place A. At this time, the express train is driving from place B to place A. The two cars meet after 2 hours. The speed of the express train is known to be 50 kilometers per hour. Find the distance between A and B.
慢车从甲地开往乙地，开出1小时后，离甲地40千米，这时，快车从乙地开往甲地，快车开出2小时后两车相遇．已知快车的速度为每小时50千米．求甲乙两地的距离．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 40</gadget>
<output>120</output>

<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<gadget id="calculator">120 + 100</gadget>
<output>220</output>

<result>220</result>