My approach for the question


#1

Think in powers of two as 2^1 (first day)
2^2(second day)

2^13
2^14
2^15
Now 1/4th of 2^15 is 2^15/2^2 (as 25% is 1/4=1/2^2) so, answer is 2^13 i.e. 13th day.