Now there are three ships sailing from Shanghai to Japan. Ship A leaves at 6 am and travels 20 kilometers per hour; ship B departs at 8 am and travels 25 kilometers per hour; ship C leaves at 9 am and travels 5 hours later After catching up with ship B, how many hours can ship C catch up with ship A?
现在有三艘轮船，从上海开往日本，甲船早上6点开出，每小时行20千米；乙船8点开出，每小时行25千米；丙船9点开出，5小时后追上乙船，丙船再行驶多少小时可追上甲船．
<gadget id="calculator">25 / 5</gadget>
<output>5</output>

<gadget id="calculator">25 + 5</gadget>
<output>30</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 * (3/10)</gadget>
<output>6</output>

<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<result>1</result>