A pile of coal weighs 90 tons. It is transported away for the first time (3/5), and it is transported for the second time (5/9). How many tons is transported for the second time?
一堆煤重90吨，第一次运走(3/5)，第二次运走的是第一次的(5/9)，第二次运走多少吨？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">90 * (3/5) * (5/9)</gadget>
<output>30</output>

<result>30</result>