There is a batch of cement at the construction site, 2/5 of this batch of cement is used up on the first day, 120 bags are used up on the second day, and there are 30 bags left. How many bags are there in this batch of cement?
建筑工地有一批水泥，第一天用去这批水泥的(2/5)，第二天用去120袋，还剩30袋．这批水泥原有多少袋？
<gadget id="calculator">120 + 30</gadget>
<output>150</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">150 / (3/5)</gadget>
<output>250</output>

<result>250</result>