The school held a "small production" competition. The third grade has 60 participants, 15 fewer than the fourth grade, and the fifth grade has twice the total number of third and fourth grade participants. How many fifth graders are participating?
学校举行"小制作"比赛．三年级有60人参赛，比四年级的人数少15人，五年级参赛的人数是三、四年级参赛总人数的2倍．五年级有多少人参赛？
<gadget id="calculator">60 + 60 + 15</gadget>
<output>135</output>

<gadget id="calculator">135 * 2</gadget>
<output>270</output>

<result>270</result>