Given: Total student = 12 Replaced student weight = 40kg Increment in average = 1kg Concept: Average = Total sum/ Total persons Calculation: Let average age of 12 students = a Sum of age of 12 students = 12a Old student weight = 40 New student weight = N New average weight = a + 1 ∴ (12a — 40 + N)/12 = a + 1 ⇒ 12a — 40 + N = 12a + 12 ⇒ 12a —40 + N = 12a + 12 ⇒ N = 12 + 40 ⇒ N = 52 New student weight = 52 kg