Ye Ming drove from his hometown to his grandfather's house 400 kilometers away, and he drove the whole journey in the first two hours (2/5). Based on this calculation, how many hours will it take Ye Ming to reach his grandfather's house.
叶明开车从自己老家开往400千米外的外公家，前两个小时行了全程的(2/5)，照这样计算，叶明还需要多少个小时才能到外公家．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / (2/5)</gadget>
<output>5</output>

<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<result>3</result>