Question

The mean weight of 25 students of a class is 52. If the mean of first 13 students is 48 kg and that of last 13 students is 55 kg. Find the weight of 13 students.​

Answer 1

Answer:

D

48 kg

Let the weight of 13th student =x

Weight of 25 students =2×4=1200

Weight of first 13 students =1×5=650

Weight of last 13 students =1×4=598

Weight of first 13 students + weight of last 13 students = Weight of 25 students + weight of 13th student

⇒65+59=120+x

⇒x=48

Answer 2

Mean weight of 25 students = 52kg

So the total weight = 25 (52) = 1300kg

Mean weight of first 13 students = 48kg

So the total weight = 13 (48) = 624kg

Mean weight of last 13 students = 55kg

So the total weight = 13 (55) = 715kg

We know thatWeight of 13th student = total weight of the first 13 students + total weight of last 13 students – total weight of 25 students

By substituting the valuesWeight of 13th student = 624 + 715 – 1300

On further calculation

Weight of 13th student = 39kg

Therefore, the weight of the 13th student is 39kg.