Li Jian rides an electric bicycle to his grandmother's house. The outer diameter of the electric bicycle tire is 40cm, and the wheel rotates 100 times per minute. The whole journey (2/5) took 5 minutes. How many kilometers is the distance between Li Jian’s house and grandma’s house?
李建骑电动车去外婆家，电动车轮胎的外直径是40cm，车轮每分钟转动100周．5分钟行了全程的(2/5)，李健家与外婆家相距多少千米？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">5 / (2/5) / 1_000</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">3.14 * (2/5) * 100 * (1/80)</gadget>
<output>1.57</output>

<result>1.57</result>