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 = 65.966+57x66+x65.966+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