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Option 4 : 52 kg
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
Shortcut Trick
Formula used:
Weight of new student = Previous average weight + increase in average weight × number of students.
Calculations:
Weight of the new student = 40 + 1 × 12 = 52 kg
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