CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon
MyQuestionIcon
Question

The mean of 35 observations is 20, out of which mean of first 18 observations is 15 and mean of last 18 observation is 25. Find the 18th observation.

Open in App
Solution

We have,

The mean of 35 observations is 20.
Let x be the sum of 35 observations

mean = sum of observations number of observations
20=x35x=700

Let y be the sum of first 18 observations.
Mean of first 18 observations is 15.
y18=15y=270
And z be the sum of last 18 observations
Mean of last 18 observations is 25.
z18=25z=450
let the 18th term be a.
18th term is common in first 18 and last 18 observations
x+a=y+z700+a=270+450a=720-700a=20
Hence, the 18th observation is 20.

flag
Suggest Corrections
thumbs-up
6
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Mean
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon