Xiao Ming did 20 math problems in 4 minutes, so how many minutes does it take on average for each problem?
小明4分钟做了20道口算题，那么平均每做一题需要多少分钟．
<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>