There is a pile of cement, 25% of the total amount is used for the first time, and 45% of the total amount is used for the second time, leaving 450 kilograms. How many kilograms are there in this pile of cement?
有一堆水泥，第一次用去总数的25%，第二次用去总数的45%，还剩下450千克，这堆水泥原有多少千克？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (1/4) - (9/20)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">450 / (3/10)</gadget>
<output>1_500</output>

<result>1_500</result>