A car travels from place A to place B for 0.4 hours, which is 20% of the journey. If, go another 30 kilometers just to reach the midpoint of the two places. So, how many kilometers are there from A to B?
一辆汽车从甲地到乙地行驶了0.4小时，这时已行全程的20%．如果，再行30千米正好到达两地的中点．那么，甲地到乙地共有多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">30 / (3/10)</gadget>
<output>100</output>

<result>100</result>