The store buys a batch of pens at a price of 10 yuan each, and sets the price at a profit of 20%. When (4/5) of this batch of pens is sold, the profit has already been 200 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，按20%的利润定价，当卖出这批钢笔的(4/5)时，就已经获利200元，这批钢笔共有多少支？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">200 / (4/5) / (1/5)</gadget>
<output>1_250</output>

<result>1_250</result>