Cars A and B are traveling toward each other from two cities that are 690 kilometers apart. Car A travels 60 kilometers per hour. Car A goes ahead for 1 hour before car B starts. Car B travels 80 kilometers per hour, how many hours after car A drives out and meets car B?
甲、乙两车从相距690千米的两城相向而行，甲车每小时行60千米，甲车先行1小时后乙车才出发．乙车每小时行80千米，甲车开出几小时后与乙车相遇？
<gadget id="calculator">60 * 1</gadget>
<output>60</output>

<gadget id="calculator">690 - 60</gadget>
<output>630</output>

<gadget id="calculator">60 + 80</gadget>
<output>140</output>

<gadget id="calculator">630 / 140</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) + 1</gadget>
<output>11/2 = around 5.5</output>

<result>11/2 = around 5.5</result>