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
A. 5

B. 40

C. 20

D. 10

Answer :

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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