Question : Among four students sitting in a row, the average age of the last three students is 48 years and the average age of the first three students is 50 years. If the age of the first student is 56 years, then what is the age of the last student?
Option 1: 30 years
Option 2: 40 years
Option 3: 50 years
Option 4: 60 years
Correct Answer: 50 years
Solution :
The average age of the last three students = 48
The sum of the ages of the last three students = 48 × 3 = 144
The average age of the first three students = 50
The sum of the ages of the first three students = 50 × 3 = 150
Age of first student = 56
Let $x$ be the age of the last student.
The difference in ages of the first and last student = 150 – 144 = 6
According to the question,
$56 - x= 6$
$\therefore x= 50$
Hence, the correct answer is 50 years.
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