The black and white team of 4 explored in the deep mountains, and all their food was only enough for 15 days. On the third day, they met a team of treasure hunters in the mountains. The team had eaten up all the food on their bodies, so they distributed their food to everyone, and the amount of food for each person remained the same, only enough to eat. 4 days. So, how many people are there in the treasure hunting team encountered by the black and white team on the third day?
黑白团队4人到深山中探险，他们所有的粮食只够吃15天．第三天，他们在山中遇到了一队寻宝的人，这队人身上的粮食全部吃完了，于是他们将自己的粮食分给所有人吃，且每人吃的粮食数不变，只够吃4天．那么，第三天黑白团队遇到的寻宝队有多少人．
<gadget id="calculator">13 / 15</gadget>
<output>13/15 = around 0.866667</output>

<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">(13/15) - (4/15)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(3/5) / (1/15)</gadget>
<output>9</output>

<result>9</result>