A car travels on a plain and a mountain for 3 hours each. The speed of the car is 60 km/h on the plain and 30 km/h on the mountain. How many kilometers has it traveled in total?
一辆车在平原和山区各行驶3小时，这辆车在平原的速度是60千米/小时，在山地的速度是30千米/小时，它一共行驶了多少千米？
<gadget id="calculator">60 + 30</gadget>
<output>90</output>

<gadget id="calculator">90 * 3</gadget>
<output>270</output>

<result>270</result>