There is a batch of cement at a certain construction site. 20% of this batch of cement was used on the first day, 20 tons were used on the second day, and 10% of this batch of cement was used on the third day. The last remaining cement is this batch of cement. (1/2) 4 tons more, how many tons did this batch of cement originally have?
某工地有一批水泥，第一天用去了这批水泥的20%，第二天用去20吨，第三天用去了这批水泥的10%，最后剩下的水泥是这批水泥的(1/2)多4吨，这批水泥原来有多少吨？
<gadget id="calculator">20 + 4</gadget>
<output>24</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/5) - (1/10) - (1/2)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">24 / (1/5)</gadget>
<output>120</output>

<result>120</result>