Average of the present ages of husband, wife and their child is 38 years. At the time of birth of the child, average age of the husband and wife was 39 years. Find the present age of the child ? पति, पत्नी और उनके बच्चे की वर्तमान आयु का औसत 38 वर्ष है। बच्चे के जन्म के समय, पति और पत्नी की औसत आयु 39 वर्ष थी। बच्चे की वर्तमान आयु ज्ञात कीजिये?

Total age of 3 people = 3×38 = 114 years. At child's birth (t years ago), parents' total age = 2×39 = 78 years. Parents aged t years each: 78 + 2t = (114 - t) - t = 114 - 2t. Solving: 78 + 2t = 114 - 2t gives 4t = 36, so t = 9. Wait - this gives child's age as t = 9, but option C is 9. Let me verify: H+W+C = 114, H+W = 78 at birth. Now H+W = 78 + 2t where t is child's age. So 78 + 2t + t = 114, t = 12. Yes, B is correct.