Question

the mean of 8 numbers is 42 if one number is excluded there mean becomes 39 what will be excluded number

Answer 1

the formula for mean is sum of observation/no. of observations.
Given that,
the no. of observation=8
mean=42
if,
one number is removed
then,
no. of observations=7
mean=39
the number removed=?
39=x/7
x=39*7
x=273
the sum of observations in 2nd case=273
then, 
the sum of observations in 1st case =42*8
                                                          =336
now,
if we subtract the sum of observations in 1st case - the sum od observations in 2nd case
=336-273
=63
therefore,the number exculded is 63

Answer 2

Given :- The mean of 8 numbers is 42. If one number is excluded, their mean becomes 39. What is the excluded number ?

Solution :-

we know that,

• Mean = (sum of observations)/(Total number of observations)

so,

→ Mean = (sum of observations)/8

→ 42 * 8 = sum of observations

→ sum of observations = 336 .

now, given that, 1 number is excluded .

then,

→ Total numbers = 8 - 1 = 7

→ Mean = 39

therefore,

→ sum of observations = Mean * Total numbers = 39 * 7 = 273 .

hence,

→ Excluded Number = sum of 8 numbers - sum of 7 numbers = 336 - 273 = 63 (Ans.)

∴ The Excluded Number is 63.

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