15% of the distance traveled by A in 2 hours is equal to the distance traveled by B in (1/2) hour, how much slower is B's speed than A's speed?
甲2小时行的路程的15%等于乙(1/2)小时行的路程，求乙速比甲速度慢多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) / (1/2)</gadget>
<output>3/10 = around 0.3</output>

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

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / (1/2)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>