Question

The mean weight of 25 students of a class is 60 kg. If the mean weight of the first 13 students of the class is 57 kg and that of the last 13 students is 63 kg, find the weight of the 13th student.

Answer 1

Maybe that incorrect. I am new to this. At least consider it. ‍♀️

Answer 2

Weight of 13th student is 60.

Step-by-step explanation:

We are given that the mean weight of 25 students is 60 kg and also the mean weight of first 13 students is 57 kg and that of the last 13 students is 63 kg.

As we know that Mean formula, $\bar X$ = $\frac{\sum X}{n}$

where, $\sum X$ = Total Sum of n observation

                 n = Number of observation

So, Total Sum of n observation ($\sum X$) = $\text{Mean} (\bar X) \times \text{Number of observation} (n)$

So, Total Sum of weight all 25 students = $60 \times 25 = 1500$ kg

Total Sum of weight of first 13 students = $57 \times 13=741$ kg

Total Sum of weight of last 13 students = $63 \times 13=819$ kg

Note: Total Sum of weight of first 13 students + Total Sum of weight of last 13 students = Total Sum of weight of all 25 students + Weight of 13th student in data

So,  741 kg + 819 kg = 1500 kg + Weight of 13th student

Therefore, Weight of 13th student = 1560 kg - 1500 kg = 60 kg.