A passenger ship sails from A to B. It is known that the distance between A and B is 270 kilometers. It takes 9 hours for the passenger ship to sail from A to B at a speed of 27 kilometers per hour. What is the speed of the water in kilometers per hour? ?
客轮从甲地开往乙地，已知甲乙两地相距270千米，客轮从甲地顺水以每小时27千米的速度航行到乙地要用9小时，这样水速度是每小时多少千米？
<gadget id="calculator">270 / 9</gadget>
<output>30</output>

<gadget id="calculator">30 - 27</gadget>
<output>3</output>

<result>3</result>