Given: In a group 100 members knows Hindi, 50 knows Urdu and 25 of them Hindi and Urdu We have to find the number of members in the group- Let H be the set of persons who speak Hindi and U be the set of persons who speak Urdu. ∴ n 〔H) = 100, n (U) = 50 and n (H ∩ U) = 25 From addition theorem of sets, we can write n(H ∪ U) = n(H) + n(U) - n (H ∩ U) Using given values ⇒ (H ∪ U) = 100 + 50 - 25 = 125 Total number of members in the group = 125 Hence, option 'C' is correct