There are (21/2) tons of rice in the grain store, and (1/3) are sold on the first day, and (4/7) of the first day are sold on the second day. How many tons were sold the next day?
粮店存有大米(21/2)吨，第一天卖出(1/3)，第二天卖出的是第一天的(4/7)．第二天卖出多少吨？
<gadget id="calculator">21 / 2</gadget>
<output>21/2 = around 10.5</output>

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

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(21/2) * (1/3) * (4/7)</gadget>
<output>2</output>

<result>2</result>