Question

mean of 7 numbers is 42 if one number is excluded there mean becomes 39 what is the number Express

Answer 1

Mean of 7 numbers = 42
Then, the sum of 7 numbers = 7×42
= 294
Let the number excluded = x
then the sum of 6 numbers = 294 - x
Mean of 6 numbers = 39

294 - x ÷ 6 = 39
294 - x = 39 ×6
294 - x = 234
x = 294 - 234
x = 60

Answer 2

The excluded number is 60.

Step-by-step explanation:

Formula for Mean

$Mean=\dfrac{\sum x}{n}$

where, $\sum x$ is the sum of observation and n is number of observations.

It is given that mean of 7 numbers is 42.

$42=\dfrac{\sum x}{7}$

Multiply both sides by 7.

$294=\sum x$

If one number is excluded there mean becomes 39.

Numbers of remaining observations = 7-1 = 6

Let the unknown number be x.

The sum of observation after excluded a number = 294 - x

$Mean=\dfrac{294-x}{6}$

$39=\dfrac{294-x}{6}$

Multiply both sides by 6.

$234=294-x$

$x=294-234$

$x=60$

Therefore, the excluded number is 60.

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