Pharaoh rides a bicycle from A to B to send documents. When he goes there with the wind, he travels 240 meters per minute. When he comes back against the wind, he travels 120 meters per minute. His average speed back and forth is how many meters per minute.
老王骑自行车从甲地去乙地送文件，去时顺风，每分钟行240米，回来时逆风，每分钟行120米．他往返的平均速度是每分钟行多少米．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 240</gadget>
<output>1/240 = around 0.004167</output>

<gadget id="calculator">1 / 120</gadget>
<output>1/120 = around 0.008333</output>

<gadget id="calculator">(1/240) + (1/120)</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">2 / (1/80)</gadget>
<output>160</output>

<result>160</result>