A car travels from city A to city B at 45 km per hour and arrives in 4 hours. When coming back, the speed is increased (1/9), how much time will it take? (answer with ratio)
一辆汽车由甲城去乙城，每小时行45km，4h到达．回来时，速度提高(1/9)，需要多少时间？(用比例解答)
<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">45 * (1/9)</gadget>
<output>5</output>

<gadget id="calculator">45 + 5</gadget>
<output>50</output>

<gadget id="calculator">180 / 50</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>