If a product is sold at a 10% discount after the purchase price is increased by 20%, and the profit is 20 yuan, what is the purchase price?
一件商品在进价的基础上提价20%后，又以9折出售，获利20元，则进价是多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(6/5) * (9/10)</gadget>
<output>27/25 = around 1.08</output>

<gadget id="calculator">(27/25) - 1</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">20 / (2/25)</gadget>
<output>250</output>

<result>250</result>