A pile of coal burned (1/4) of the total on the first day and (2/5) of the total on the second day, leaving 490 kilograms. How many kilograms are there in this pile of coal?
一堆煤，第一天烧了总数的(1/4)，第二天烧了总数的(2/5)，还剩下490千克，这堆煤一共有多少千克？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">490 / (7/20)</gadget>
<output>1_400</output>

<result>1_400</result>