It's a bit long, but this was my approach. Would love to see shortcuts, if any.Let number of students who studied French yesterday be represented by F
(3/4)*F must be an integer => F=4n
YesterdayTotal no. of students = F = 4n
No. of students born before 2000 = (3/4)F = 3n
TodayTotal no. of students = F+44 = 4n+44
Now these additional 44 students could belong to the group which was born before 2000 or may be some part of them could belong to the group.
Let the additional students who were born before 2000 be represented by x
No. of students born before 2000 = 3n + x
We also know that today the ratio is 4/5
=> 4/5 = (3n+x) / (4n +44)
=> 16n + 176 = 15n + 5x
=> n = 5x - 176
The ratio is changing from 3/4 to 4/5. The ratio is increasing in value.
This means that we need to consider that more than 3/4 of the new 44 students i.e 33 were born before 2000.
With x = 34, 5x - 176 is negative => Invalid
With x = 35, 5x - 176 is negative => Invalid
With x = 36, 5x - 176 is POSITIVE => VALID
Therefore x can be 36, 37, 38, 39, 40, 41, 42, 43, 44
Median = 40
Remember, the question is asking for the no. of students today who were born before 2000 which are given by 3n +x
= 15x - 528 + x
= 16x - 528
= 16*40 - 528
= 112
Therefore, answer is B 112.