In a box of beads for the first time, take out (1/5) and 4 of the total number, take out the remaining (1/4) and 3 for the second time, and take out the remaining (1/3) and 2 for the third time 1, take out the remaining (1/2) and 1 for the fourth time, and then there is 1 left in the box? How many original beads are in the box?
第一次在一盒珠子中，取走总数的(1/5)又4个，第二次取出余下的(1/4)又3个，第三次取出余下的(1/3)又2个，第四次取出余下的(1/2)又1个，这时盒里还剩1个？问盒内原有珠子多少个﹖
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / (1/2)</gadget>
<output>4</output>

<gadget id="calculator">4 + 2</gadget>
<output>6</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">6 / (2/3)</gadget>
<output>9</output>

<gadget id="calculator">9 + 3</gadget>
<output>12</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">12 / (3/4)</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

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

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 / (4/5)</gadget>
<output>25</output>

<result>25</result>