A product is sold at a reduced price according to the season. If the current price is reduced by 10%, a profit of 360 yuan can still be made; if the price is reduced by 20%, a loss of 480 yuan will be incurred. How much is the purchase price of this product?
一件商品随季节变化降价出售．如果按现价降价10%，仍可获利360元；如果降价20%，就要亏损480元，这件商品的进价是多少元？
<gadget id="calculator">360 + 480</gadget>
<output>840</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">(1/5) - (1/10) - 1</gadget>
<output>-9/10 = around -0.9</output>

<gadget id="calculator">1 + (-9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">840 / (1/10)</gadget>
<output>8_400</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">8_400 * (9/10)</gadget>
<output>7_560</output>

<gadget id="calculator">7_560 - 360</gadget>
<output>7_200</output>

<result>7_200</result>