A puzzle on Facebook (Source: XAT-2013)

January 25th, 2013 by

Sara has just joined Facebook. She has 5 friends. Each of her five friends has twenty five friends. It is found that at least two of Sara’s friends are connected with each other. On her birthday, Sara decides to invite her friends and the friends of her friends. How many people did she invite for her birthday party? (A)  ≥ 105  (B) ≤ 123        (C) ≥ 125        (D) ≥ 100 and ≤ 125 (E) ≥ 105 and ≤ 123 Solution:  The key point: “Each of Sara’s 5 friends has twenty five friends” => Sara is one among these 25 friends.