A circular pool has an inner diameter of 10 meters and a depth of 2 meters. The pool is equipped with 5 similar water inlet pipes, each of which can inject 7.85 cubic meters of water per hour. How many hours can the pool be filled with all five pipes?
一个圆形水池，它的内直径是10米，深2米，池上装有5个同样的进水管，每个管每小时可以注入水7.85立方米，五管齐开几小时可以注满水池？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25 * 2</gadget>
<output>157</output>

<gadget id="calculator">7.85 * 5</gadget>
<output>39.25</output>

<gadget id="calculator">157 / 39.25</gadget>
<output>4</output>

<result>4</result>