From a certain day, the floating weeds on the surface of the pond doubled every day. After 50 days, the whole pond was covered with floating weeds. On the number of days, the area occupied by duckweed was (1/4) of the pond.
从某天起，池塘水面上的浮草，每天增加一倍，50天后整个池塘长满了浮草，第多少天时浮萍所占面积是池塘的(1/4)．
<result>48</result>