There is a batch of cement at a construction site, 40% of the total amount is transported on the first day, and 35% of the total amount is transported on the first day, and 15 tons more are transported on the first day than on the second day. How many tons are there in this batch of cement?
某工地有一批水泥，第一天运走总量的40%，第一天运走总量的35%，第一天比第二天多运走15吨，这批水泥有多少吨？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(2/5) - (7/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">15 / (1/20)</gadget>
<output>300</output>

<result>300</result>