Average age of seven persons in a group is 30 years . the average age of five persons of this group is 31 years. What is the average age of the other two persons in the group ? एक ग्रुप में सात व्यक्तियों की औसत आयु 30 वर्ष है , उस ग्रुप के पांच व्यक्तियों की औसत आयु 31 वर्ष है | ग्रुप के अन्य दो व्यक्तियों की औसत आयु कितनी है ?

Total age of 7 persons = 7 × 30 = 210 years. Total age of 5 persons = 5 × 31 = 155 years. Age of remaining 2 persons = 210 - 155 = 55 years. Average = 55/2 = 27.5 years. Option A (26 years) is incorrect. Option B (15 years) would mean the two persons are very young, making the others much older. Option C (55 years) is the sum, not the average. Since 27.5 is not listed, D is correct.