Answer:
46 days
Explanation:
It is a very logical question which does not require any mathematical calculation rather requires thinking.
It is said in the question every day, the patch doubles in size. if it takes 48 days for the patch to cover the entire lake.
Let total area of the lake be 100 m^2. The at the end of 48th day, it would have covered 100 m^2. So, at the end of 47th day it would have covered only 50 m^2, since every day, the patch doubles in size. Similarly on 46th day it would have covered 25 m^2, which is quarter of 100 m^2.
So ,it would take 46 days for the patch to cover quarter the lake.
