Question

xample 5:
The mean of seven observations is 25. The mean of first four observations is 23
and the mean of last four observations is 29. Find the fourth observation.​

Answer 1

Let the numbers are x1,x2,x3, x4,x5,x6,x7

Mean = Sum of all observation/Total number of observation

x1+x2+x3+x4+x5+x6+x7=25×7

x1+x2+x3+x4+x5+x6+x7=175...eq1

ATQ

x1+x2+x3+x4= 23×4

x1+x2+x3+x4=92...eq2

x4+x5+x6+x7=29×4

x4+x5+x6+x7= 116...eq3

Since eq1=eq2+eq3

but here x4 is added twice,so to find x4

x4=116+92-175

x4=208-175

x4=33

Hope it helps you.