A car drove from Yinchuan to Shizuishan, traveled the whole distance (1/4) in the first hour, traveled 50 kilometers in the second hour, and traveled 50% of the distance in two hours. How many kilometers is the distance from Yinchuan to Shizuishan?
一辆汽车从银川开往石嘴山，第一小时行了全程的(1/4)，第二小时行了50千米，两个小时共行了全程的50%．银川到石嘴山的距离是多少千米？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) - (1/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">50 / (1/4)</gadget>
<output>200</output>

<result>200</result>