The school holds a sports meeting. The third grade has 45 participants, the fourth grade has 7 more participants than the third grade, and the fifth grade has twice the total number of third and fourth grade participants. How many fifth graders are participating?
学校举行运动会．三年级有45人参赛，四年级参赛人数比三年级多7人，五年级参赛人数是三、四年级参赛总人数的2倍．五年级有多少人参赛？
<gadget id="calculator">45 + 7 + 45</gadget>
<output>97</output>

<gadget id="calculator">97 * 2</gadget>
<output>194</output>

<result>194</result>