On a map with a scale of 1:4000000, the distance between ports A and B is 9 cm. A cargo ship sails from port A to port B at 6 am at a speed of 24 kilometers per hour. The time it arrives at port B is How many.
在比例尺是1：4000000的地图，量得A、B两港的距离9厘米，一艘货船于上午6时以每小时24千米的速度从A港开向B港，到达B港的时间是多少．
<gadget id="calculator">1 / 4_000_000</gadget>
<output>1/4_000_000 = around 0</output>

<gadget id="calculator">9 / (1/4_000_000) / 100_000 / 24</gadget>
<output>15</output>

<gadget id="calculator">6 + 15</gadget>
<output>21</output>

<result>21</result>