From A to B, a car traveled 210 kilometers in the first 3 hours. At this speed, it took another 4 hours to reach B. How many kilometers are there in total from A to B? (Solution by proportional method)
从甲地到乙地，一辆汽车前3小时走了210千米，照这样的速度，又走了4小时到达乙地，求甲地到乙地共多少千米？(用比例方法解)
<gadget id="calculator">210 / 3</gadget>
<output>70</output>

<gadget id="calculator">70 * 3</gadget>
<output>210</output>

<gadget id="calculator">70 * 4</gadget>
<output>280</output>

<gadget id="calculator">210 + 280</gadget>
<output>490</output>

<result>490</result>