A certain beach salt field used 500 tons of seawater to obtain 22.5 tons of salt. Find the salinity of seawater in this area.
某海滩盐场，用500吨海水晒得22.5吨盐．求这个海域的海水含盐率．
<gadget id="calculator">22.5 / 500</gadget>
<output>0.045</output>

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

<gadget id="calculator">0.045 * 1</gadget>
<output>0.045</output>

<result>0.045</result>