Question

the mean of 15 numbers is 8.5 and means of 25 numbers is 11.5. Determine the mean of 40 numbers taken together
​

Answer 1

Step-by-step explanation:

We know that:-

mean of n observations = { sum of n observations } / n

From here,

Sum of n observations = mean × n

Here,

According to given

sum of Frist 15 number = 8.5 × 15 = 127.5

&

Sum of next 25 = 11.5 × 25 = 287.5

Here,

Sum of Frist 40 = 127.5 + 287.5 = 415

Now,

mean (Frist 40 observations) = 415 / 40 => 10.375

=> 10.375 Answer

Hope it helps.. :-)