and B ride bicycles from city A to city B at the same time. A travels 12 kilometers per hour and B travels 9 kilometers per hour. A stayed on the way for 4 hours, so A arrived 1 hour later than B. How many kilometers is the distance between the two cities of AB?
甲乙两人同时骑自行车由A城到B城．甲每小时行12千米，乙每小时行9千米．甲在途中停留了4小时，因此甲比乙迟到1小时．问AB两城相距多少千米？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/9) - (1/12)</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">3 / (1/36)</gadget>
<output>108</output>

<result>108</result>