A train travels 637 kilometers in 7 hours. At this speed, it takes 21 hours to travel from A to B. How many kilometers are there between A and B?
一列火车7小时行驶637千米，照这样的速度，从甲地到乙地需要21小时，甲、乙两地相距多少千米？
<gadget id="calculator">637 / 7</gadget>
<output>91</output>

<gadget id="calculator">91 * 21</gadget>
<output>1_911</output>

<result>1_911</result>