42 tons of grass are dried in the pasture, and 25.2 tons of hay are obtained as a result. Find the moisture content of the grass.
牧场晒42吨青草，结果得到25.2吨干草，求青草的含水率．
<gadget id="calculator">42 - 25.2</gadget>
<output>16.8</output>

<gadget id="calculator">16.8 / 42</gadget>
<output>0.4</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">0.4 * 1</gadget>
<output>0.4</output>

<result>0.4</result>