Xiao Ming's mother bought a total of 60 roosters and chicks at the market for 60 yuan, two chickens for one yuan, and one rooster for two yuan. How many chickens did Xiao Ming's mother buy at the market.
小明的妈妈在集市上用60元共买了60只公鸡和小鸡，小鸡一元两只，公鸡二元一只，小明的妈妈在集市上买了多少只小鸡．
<gadget id="calculator">2 * 60</gadget>
<output>120</output>

<gadget id="calculator">120 - 60</gadget>
<output>60</output>

<gadget id="calculator">2 - 0.5</gadget>
<output>1.5</output>

<gadget id="calculator">60 / 1.5</gadget>
<output>40</output>

<result>40</result>