The distance between A and B is 48 kilometers. It takes 3 hours for a boat to go from A to B along the river. The return time is 8 hours due to the flooding after the rain. The normal water speed is 4 Kilometers, how much does the water speed increase after flooding?
甲、乙两地相距48千米，一船顺流由甲地去乙地，需航行3小时；返回时间因雨后涨水，所以用了8小时才回到乙地，平时水速为4千米，涨水后水速增加多少？
<gadget id="calculator">48 / 3</gadget>
<output>16</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<gadget id="calculator">48 / 8</gadget>
<output>6</output>

<gadget id="calculator">12 - 6</gadget>
<output>6</output>

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

<result>2</result>