It took the postman 3 hours to deliver the letter to the mountain area, and the return speed was 20% faster than the time when he went. How many hours did it take to return.
邮递员为山区送信，去时用了3小时，返回时的速度比去时快20%．返回时用了多少小时．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(1/3) * (6/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / (2/5)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>