There are three litters of rabbits, each with 30 rabbits, the first litter has as many white rabbits as the second litter has black rabbits, and the third litter has (1/3) black rabbits, how many rabbits are there in total? black rabbit.
有三窝兔子，每窝都有30只，第一窝中的白兔与第二窝中的黑兔同样多，第三窝有(1/3)是黑兔，这三窝兔子一共有多少只黑兔．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 * 2 * (1/2)</gadget>
<output>30</output>

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

<gadget id="calculator">30 * (1/3)</gadget>
<output>10</output>

<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<result>40</result>