A cuboid glass fish tank is 50 cm long, 40 cm wide and 30 cm high when measured from the inside. First pour 40L of water into the fish tank, then put pebbles, aquatic plants and fish in it, and the water level rises to 23.5cm. What is the total volume of these pebbles, aquatic plants and fish?
一个长方体玻璃鱼缸，从内部测量长50cm米，宽40cm，高30cm．先往鱼缸里注入40L水，再往里放鹅卵石、水草和鱼，水面上升到23.5cm．这些鹅卵石、水草和鱼的体积一共是多少？
<gadget id="calculator">50 * 40 * 23.5</gadget>
<output>47_000</output>

<gadget id="calculator">40 * 1_000</gadget>
<output>40_000</output>

<gadget id="calculator">47_000 - 40_000</gadget>
<output>7_000</output>

<result>7_000</result>