What is the product of the sum of (1/4) and (1/5) multiplied by their difference?
(1/4)与(1/5)的和乘以它们的差，积是多少？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(9/20) * (1/20)</gadget>
<output>9/400 = around 0.0225</output>

<result>9/400 = around 0.0225</result>