It is known that the sum of the sides of a cuboid is 84cm, and the ratio of length, width and height is 3:2:1. What is the volume of this cuboid?
已知一个长方体的棱长和为84cm，长、宽、高的比是3：2：1，这个长方体的体积是多少？
<gadget id="calculator">84 / 4</gadget>
<output>21</output>

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

<gadget id="calculator">3 / 6</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">21 * (1/2)</gadget>
<output>21/2 = around 10.5</output>

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

<gadget id="calculator">21 * (1/3)</gadget>
<output>7</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">21 * (1/6)</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(21/2) * 7 * (7/2)</gadget>
<output>1_029/4 = around 257.25</output>

<result>1_029/4 = around 257.25</result>