The store buys a batch of pens at a price of 10 yuan each, and then sells them at a fixed price after adding 40% of the profit. When (1/4) of the batch of pens is left, it has already made a profit of 240 yuan. How many pens are there in this batch?
商店以每支10元的价格购进一批钢笔，加上40%的利润以后定价出售，当还剩这批钢笔的(1/4)时就已经获利240元．这批钢笔共有多少支？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">10 * (2/5)</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">240 / 4 / (3/4)</gadget>
<output>80</output>

<result>80</result>