fish tank is 30 cm long, 50 cm wide, and 35 cm high from the inside. If 30 liters of water are placed in it, what is the height of the water surface in cm?
一个鱼缸从里面量长30厘米，宽50厘米，高35厘米，若往里面放30升水，水面的高度是多少厘米．
<gadget id="calculator">30 * 50</gadget>
<output>1_500</output>

<gadget id="calculator">1_000 / 1_500</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 * (2/3)</gadget>
<output>20</output>

<result>20</result>