Haohao and Tongtong participated in the environmental protection award activity together: 5 waste batteries can be exchanged for 2 chances of lucky draw, Haohao picked up 12 waste batteries, Tongtong picked up 8 waste batteries, they added up to exchange for 8 lucky chances In the end, they won 6 prizes and received 15 water-based pens. What is their winning rate this time?
浩浩和童童一起参加环保有奖活动：5个废电池可以换2次摸奖机会，浩浩捡了12个废电池，童童捡了8个废电池，他们加起来正好换得8次摸奖机会，结果中奖6次，领到15支水性笔，他俩这次的中奖率是多少？
<gadget id="calculator">6 / 8</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>