2 / √5, 3 / 5, 4 / 5√5, 5 / 25,(.....)
Clearly, the numerators of the given fraction are consecutive natural numbers.
So, the numerator of the missing fraction should be 6.
Also, the denominator of each fraction is multiplied by
√5 to obtain the denominator of the next fraction.
So, the denominator of the missing fraction should be 25√5.