Question

the mean of 35 observation is 20 ,our of which mean is first 18
observation is 15 and mean of last observation is 25 find the 18th of the nation ​

Answer 1

As there are 35 observations, in the above means there is repetition of 18th observation in both.

Therefore,

18th no. = mean of last 18 observations- mean of first 18 observations.

= 25-20

18th no. = 5