Q. 104.8( 4 Votes )
The mean of 5 numbers is 20. If one number is excluded their mean is 15. Then the excluded number is
Given that, Total number of observations = 5
Mean = 20
So, Sum of observations can be given as
Sum of observations = Mean × Total number of observations [∵ ]
⇒ Sum of observations = 20 × 5
⇒ Sum of observations = 100
Let the excluded number be x.
New Sum of observations = 100 – x
New Mean = 15
New total number of observations = 4
Mean is given by
⇒ 100 – x = 15 × 4
⇒ 100 – x = 60
⇒ x = 100 – 60 = 40
⇒ The excluded number is 40.
Thus, option (B) is correct.
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