Uncle Wang walks 50 meters per minute from his home to work, and he can get there in 12 minutes. If he walks 40 meters per minute now, how much longer does it take now than before?
王叔叔从家到单位，每分钟步行50米，12分钟可以到达，如果现在每分钟步行40米，现在用的时间比原来多几分之几？
<gadget id="calculator">12 / 40</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">50 * (3/10)</gadget>
<output>15</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">3 / 12</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>