The engineering team mixed cement, yellow sand, and stones into concrete at a mass ratio of 2:3:5. There are currently 2.7 tons of cement, yellow sand, and gravel. If the yellow sand is just used up, how many tons of gravel are still missing?
工程队将水泥、黄沙、石子按2：3：5的质量比拌成混凝土．现有水泥、黄沙、石子各2.7吨，如果黄沙刚好用完，那么石子还缺多少吨？
<gadget id="calculator">2.7 / 3</gadget>
<output>0.9</output>

<gadget id="calculator">0.9 * 5</gadget>
<output>4.5</output>

<gadget id="calculator">4.5 - 2.7</gadget>
<output>1.8</output>

<result>1.8</result>