Calculation: 2*(1/4)+4*(1/6)+6*(1/8)+8*(1/10)...+48*(1/50).
计算：2*(1/4)+4*(1/6)+6*(1/8)+8*(1/10)…+48*(1/50)．
<gadget id="calculator">1 / 25</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">1 + (1/25)</gadget>
<output>26/25 = around 1.04</output>

<gadget id="calculator">25 / 2</gadget>
<output>25/2 = around 12.5</output>

<gadget id="calculator">(26/25) * (25/2)</gadget>
<output>13</output>

<gadget id="calculator">25 - 13</gadget>
<output>12</output>

<result>12</result>