Question

The average weight of 15 students is 50 kg. If by mistake the weight of one of the students was noted as 80 kg instead of 50 kg, then the correct average weight of the students is

• A. 57 kg
• B. 48 kg
• C. 44 kg
• D. 50 kg

Answer 1

The correct option is B 48 kg

Average weight = $\frac{\text{Total weight of the students}}{\text{Total number of students}}$
Here, 50 =$\frac{\text{Sum of weights of 15 students}}{15}$
$\Rightarrow$ Sum of weights of 15 students = 50 × 15 = 750 …..(i)
Weight of one student was taken 80 kg instead of 50 kg.
$\therefore \text{New average}=\frac{\text{Sum of weights of 15 students - 80 + 50}}{15}$
$=\frac{750-80+50}{15}$ [from(i)]
$=\frac{750-30}{15}$
$=\frac{720}{15}$
= 48 kg
Hence, the correct answer is option (b).