What is the product of the quotient of 15 divided by 30 times the difference between (1/4) and (1/5)?
15除以30的商乘(1/4)与(1/5)的差，积是多少？
<gadget id="calculator">15 / 30</gadget>
<output>1/2 = around 0.5</output>

<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>1/20 = around 0.05</output>

<gadget id="calculator">(1/2) * (1/20)</gadget>
<output>1/40 = around 0.025</output>

<result>1/40 = around 0.025</result>