RRB Group-D Model Paper 20 with answers for online practice

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