Liu Dan goes to school from home. If he walks 3.5 kilometers per hour, he will arrive in 0.8 hours. If he walks 4 kilometers per hour, how many hours will it take to get to school?
刘丹从家去学校，如果每小时走3.5千米，0.8小时到达，如果每小时走4千米，要多少小时到学校？
<gadget id="calculator">0.8 / 4</gadget>
<output>0.2</output>

<gadget id="calculator">3.5 * 0.2</gadget>
<output>0.7</output>

<result>0.7</result>