Concept: The question tests on basics of Averages
Solution:
Let the number of female students = x
Sum of ages of the male students = 65.9 * 66
Sum of ages of the female students = 57x
Therefore Average = 60.3 = Sum of observations / total observations = 65.9∗66+57x66+x65.9∗66+57x66+x
66 * 60.3 + 60.3x = 65.9 * 66 + 57x
3.3x = 66 * (65.9 - 60.3)
x = (660 / 33) * (5.6) = 20 * 5.6 = 112
Option A