Question

The mean of four numbers is 50.If one more number is included, the mean will still remain 50.Find the number included​

Answer 1

Mean = Sum of all observations/total no. of observations

50=sum of all observations/9

Sum of all observations=450

If one number is added, mean = 55

Now, total no. of observations = 9+1=10

Let the included number be x.

Therefore, 55=Sum of all earlier observations + x/10

55=450+x/10

550=450+x

x=550-450

x=100