#### Question

Mean of 100 observations is 40. The 9th observation is 30. If this is replaced by 70 keeping all other observations same, find the new mean.

40.6

40.4

40.3

40.7

#### Solution

We have,

Mean of 100 observations is 40.

Total sum of observations = 100 x 40 = 4000

If the 9th observation is 30 and is replaced by 70 keeping all other observations same.

New, total sum of observations = 4000 - 30 + 70 = 4040

So, the new mean = `4040/100` = 40.4

Mean of 100 observations is 40.

Total sum of observations = 100 x 40 = 4000

If the 9th observation is 30 and is replaced by 70 keeping all other observations same.

New, total sum of observations = 4000 - 30 + 70 = 4040

So, the new mean = `4040/100` = 40.4

Hence, the correct alternative answer is (B).

Is there an error in this question or solution?

Solution Mean of 100 Observations is 40. the 9th Observation is 30. If this is Replaced by 70 Keeping All Other Observations Same, Find the New Mean. Concept: Measures of Central Tendency.