This question was reported to be very popular among the candidates and they perform well in it.  Majority of them were reported to have obtained the full marks.  It was also observed that majority of the candidates listed the odd numbers before adding them instead of using the method of Arithmetic Progression (A.P) in which case they would apply the formulae
Tn = a +(n-1)d and Sn = (2a + (n-1)d).  Where n = number of terms, a = first term, Tn = 𝑙 = 99, Sn = sum of the first n terms and d = 2.  The number of odd numbers between 51 and 99 = n =  + 1 =  = 25.  Therefore the required sum, Sn =  =  = 1875.