Question

The average weight of students in a class of 35 students is 40 kg. If the weight of the teacher be included, the average rises by $\frac{1}{2}$kg; the weight of the teacher is

• A. 40.5 kg
• B. 50 kg
• C. 41 kg
• D. 58 kg

Answer 1

Answer: (D)

58 kg

Answer 2

Let the weight of the teacher is w kg , then

$40 + \frac{1}{2} = \frac{35 \times 40 + w}{35 + 1}$

⇒ $36 \times 40 + 36 \times \frac{1}{2} = 35 \times 40 + w$ ⇒ $w = 58$

∴ Weight of the teacher = 58kg.