Question

The mean of 8 observation is 140. If 5 is added to each observation, then what will be the new mean

Answer 1

Answer:

Mean of observations =( Sum of all observations)/Number of observations

Given that mean of 8 observations = 140

ie. (sum of all observations)/8 =140

sum of all observations = 140×8 = 1120

When 5 is added to each observations total sum will also be added by 5

ie. now the sum of all observations = 1120+5 =1125

New mean = 1125/8 = 140.625

Answer 2

Answer:

The new mean will be 13.

Step by step answer:

We know that,

If a,b,c are three observations then,

Mean = $\frac{a+b+c + +n}{n}$ = Sum of n observations/n

According to the question,

140 = Sum / n

Adding 5 to all observations,

a+5, b+5, c+5,  n+5

Mean = $\frac{[(a+5)+(b+5)+(c+5)+ (n+5)]}{n}$

         = $\frac{[(a+b+c +n) + 5n]}{n}$

         = $\frac{(a+b+c +n)}{n} + \frac{5n}{n}$

The first term is the old mean and the second term becomes 5 on cancelling n from numerator and denominator.

         = $140 + 5$

         = $13$

Therefore,

New  = previous + 5

         = 140 + 5

         = 145