One day there was a power outage, and two candles of the same length were lit in the room at the same time. The quality of these two candles is different, one can last for 3 hours. The other can last for 5 hours. When the candle is blown out when the power is supplied, it is found that the remaining length of one of them is three times the remaining length of the other. Q: How many hours was the power outage?
某日停电，房间里同时点燃了两支同样长的蜡烛．这两支蜡烛的质量不同，一支可以维持3小时．另一支可以维持5小时，当送电时吹灭蜡烛，发现其中一支剩下的长度是另一支剩下长度的3倍．问：这次停电多少小时？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3 * (1/3)</gadget>
<output>1</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2 / (4/5)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>