The ratio of A, B, and C is 1:2:3, and their average is 30. What is the number of B?
甲、乙、丙三个数的比是1：2：3，它们的平均数是30，那么乙数是多少．
<gadget id="calculator">1 + 2 + 3</gadget>
<output>6</output>

<gadget id="calculator">2 / 6</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">30 * 3 * (1/3)</gadget>
<output>30</output>

<result>30</result>