Sailfish is a champion swimmer among animals, it can swim 30 kilometers in 20 minutes. Dolphins are also good swimmers, they can swim 60 kilometers in one hour. How many kilometers per minute do dolphins swim less than sailfish?
旗鱼是动物中的游泳冠军，它20分钟能游30千米．海豚也是游泳能手，它1小时能游60千米．每分钟海豚比旗鱼少游多少千米？
<gadget id="calculator">30 / 20</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">60 / 60</gadget>
<output>1</output>

<gadget id="calculator">(3/2) - 1</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>