Question

The average age of a teacher and three students is $20$ years. If all students are of equal age and the difference between the age of the teacher and that of a student is $20$ years, then the age of the teacher is

• A. $25$ years
• B. $30$ years
• C. $35$ years
• D. $45$ years

Answer 1

Answer: (C)

$35$ years

Let the age of each student be $x$ years
Then, the age of teacher will be $(x+20)$ years
Mean age $=\frac{(x+20)+3x}{4}$
$20=\frac{(4x+20)}{4}$
$\Rightarrow x=15$
Hence, age of the teacher $=35$ years