The distance between A and B is 300km. Cars A and B start from the two places at the same time and drive toward each other. It is known that car A travels 60km per hour. After 2.5 hours, the distance between the two cars is still 50km (the two cars have not met). How many kilometers per hour does car B travel?
A、B两地相距300km，甲、乙两车同时从两地出发，相向而行，已知甲车每时行60km，2.5时后，两车还相距50km(两车没有相遇)．求乙车每时行多少千米？
<gadget id="calculator">300 - 50</gadget>
<output>250</output>

<gadget id="calculator">250 / 2.5</gadget>
<output>100</output>

<gadget id="calculator">100 - 60</gadget>
<output>40</output>

<result>40</result>