The weight ratio of the three bags of grain A, B, and C is 3:4:5. It is known that A and B weigh 700 grams in total. What is the weight of the C bag?
甲、乙、丙三袋粮食重量比是3：4：5，已知甲、乙共重700克，求丙袋的重量是多少？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">700 / 7</gadget>
<output>100</output>

<gadget id="calculator">100 * 5</gadget>
<output>500</output>

<result>500</result>