Question

The mean of 8 observations is 7.5 and mean of another 7 observations is 15 find the mean of all the 15 observations

Answer 1

mean of 8 observations = total of 8 observations (t1) / 8
7.5 = t1/8 → t1 = 8 × 7.5 = 60
mean of 7 observations = m2 = total of 7 observations (t2) / 7
15 = t2/7 → t2 = 7 × 15 = 105
t1 + t2 = 60 + 105 = 165
avg. of 15 observations = 165/15 = 11

Answer 2

Answer:

The answer is 11.

Step-by-step explanation:

Given data

The mean of 8 observations = 7.5  

And mean of another 7 observations = 15  

Here we need to find mean of 15 observations

We know that

mean of observations = sum of observations/ No of observations

⇒ Sum of observations = mean of observations×No of observations

From given data  

mean of 8 observations = 7.5

⇒ sum of 8 observations = 7.5 × 8 = 60

mean of 7 observations = 15

⇒ sum of 7 observations = 15 × 7 = 105

sum of 15 observations = sum of 8 observations +  sum of 7 observations

                                       =  60  + 105  = 165

Therefore,

mean of 15 observations = sum of 15 observations / 15

                                          = 165/15 = 11