Xiao Ming's house is 25.5 kilometers away from grandma's house. He rides a bicycle to walk 15 kilometers per hour, and he has already walked for 1.5 hours. According to this calculation, how many hours will it take for the rest of the road?
小明家距姥姥家25.5千米．他骑自行车每小时走15千米，已经走了1.5小时，照这样计算，余下的路还需要多少小时？
<gadget id="calculator">25.5 / 15</gadget>
<output>1.7</output>

<gadget id="calculator">1.7 - 1.5</gadget>
<output>0.2</output>

<result>0.2</result>