On a map with a scale of (1/7000000), the distance from Beijing to Jinggangshan is 21cm. According to this calculation, how many kilometers is the actual distance from Beijing to Jinggangshan?
在一幅比例尺是(1/7000000)的地图上，量出北京到井冈山的距离是21cm，照这样计算，北京到井冈山的实际距离大约是多少千米？
<gadget id="calculator">1 / 7_000_000</gadget>
<output>1/7_000_000 = around 0</output>

<gadget id="calculator">21 / (1/7_000_000) / 1_000_000</gadget>
<output>147</output>

<result>147</result>