A reservoir can hold 60 tons of water, and the empty tank can be filled with water in 5 hours by opening the A pipe alone, and 8 tons of water can be injected per hour by opening the B pipe alone. If the two pipes are opened together, how many hours can the pool be filled with water?
一个蓄水池可以装60吨水，单开甲管5小时可将空池注满水，单开乙管每小时可注入水8吨．如果两管一起开，几小时可将水池注满水？
<gadget id="calculator">60 / 5</gadget>
<output>12</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<result>3</result>