The average weight of a class of students is 67.5 kg.

Ques - The average weight of a class of students is 67.5 kg. The weight of the class teacher is 25% more than the average weight of the class. The average weight of the class is less than the class teacher by x%. The value of x is:

(a) 33.33%

(b) 25%

(c) 20%

(d) Can't be determined

Solution -

The average weight of a class of students = 67.5 kg

Let,

The weight of the class teacher = Y

A/C

The weight of the class teacher = 25% more than the average weight of the class

The weight of the class teacher = 67.5 + 25% of 67.5

The weight of the class teacher = 67.5 + (25/100) × 67.5 

The weight of the class teacher = 67.5 + 16.875

The weight of the class teacher = 84.375 kg

Now,

The average weight of the class is less than the class teacher by x%.

= [( Weight of teacher - Average weight of the class ) / Weight of the teacher]× 100

= [(84.375 - 67.5) / 84.375] × 100

= [16.375 / 84.375] × 100

= 20 

Therefore,

The value of x is 20%.

Hence,

The correct answer is option (c) 20%.