(2/3) of a test field grows fruit, and the test field of watermelon is also a fruit field (2/7), so how much of the total test field is the field of watermelon?
一块试验田的(2/3)种水果，而种西瓜的试验田又是水果田的(2/7)，那么种西瓜的田占总试验田的多少．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/3) * (2/7)</gadget>
<output>4/21 = around 0.190476</output>

<result>4/21 = around 0.190476</result>