The road between Nantong and Nanjing is 210 kilometers long. Passenger cars and trucks depart from Nantong and Nanjing at the same time and drive in opposite directions. The speed ratio of passenger cars and trucks is 4:3. How many kilometers did the bus drive when they met?
南通与南京间的公路长210千米，客车与货车分别从南通和南京同时出发，相向而行，客车和货车的速度比为4：3．相遇时，客车行驶了多少千米？
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">210 * (4/7)</gadget>
<output>120</output>

<result>120</result>