In a 25-story building, A and B compete to climb the stairs. When A reaches the 9th floor, B has just reached the 5th floor. At this speed, when A reaches the top floor, how many floors does B reach?
在一幢高25层的大楼里，甲、乙两个比赛爬楼梯，甲到9楼时，乙刚上到5楼，照这样的速度，当甲到了顶层时乙到了多少楼．
<gadget id="calculator">25 - 1</gadget>
<output>24</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">8 / 4</gadget>
<output>2</output>

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

<gadget id="calculator">24 * (1/2)</gadget>
<output>12</output>

<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<result>13</result>