Due to the drought, the river narrowed. A small boat and a big boat met in a 10-kilometer narrow river. If the speed of the small ship is twice the speed of the large ship, the speed of the two ships reversing is 1/3 of their respective speeds, and the distance traveled by the small ship is 4 times that of the large ship. m/hour, then how many hours will it take for the two ships to pass through this river at least? (regardless of boat length)
由于干旱，河道变窄，一条小船与一条大船在10千米狭窄河道相遇，必须倒船让行，两船才能继续航行．如果小船速度是大船速度的2倍，两船倒船的速度都是它们各自速度的(1/3)，小船倒船的路程是大船倒船路程的4倍，已知小船的速度是25千米/小时，那么两船均要通过这段河道最少共需多少小时？(不考虑船的长度)
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">10 * (1/5)</gadget>
<output>2</output>

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

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

<gadget id="calculator">(25/2) * (1/3)</gadget>
<output>25/6 = around 4.166667</output>

<gadget id="calculator">2 / (25/6)</gadget>
<output>12/25 = around 0.48</output>

<gadget id="calculator">10 / (25/2)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(12/25) + (4/5)</gadget>
<output>32/25 = around 1.28</output>

<result>32/25 = around 1.28</result>