Question

an of first 13 observations is
1.
The mean of 25 observations is 36. Out of these observations, the mean of first
32 and that of the last 13 observations is 40. Find the 13th observation.
(2) 36
(3) 40
(1) 32
(4) 25
​

Answer 1

total mean of 25 observations is equals to 36

sum 25 observation is 25 × 36=900

sum of the mean of first 13 observations is equals to 13 × 32=416

some of the mean last 13 observations is equal to 31 × 40= 520

sum of 520+416=936

difference of 936 and 900=36