Question

i) The arithmetic mean of 9 observations is 100 and that of 6 is 80, the combined mean of all the 15 observations will be (a) 100 (b) 80 (C) 90 (d) 92 ​

Answer 1

Step-by-step explanation:

the ⇒ Given mean of 9 observations =100

⇒ Mean=

numberofobservations

sumofobservations

⇒ 100=

9

sumofobservations

∴ Sum of observations =9×100=900

⇒ Similarly sum of observations of other data =6×80=480

⇒ Sum of observations of both the data =900+480=1380

⇒ Total number of observations =9+6=15

⇒ New mean =

15

1380

=92

∴ The mean of all the 15 observati

Answer 2

Hence, combined mean of all the 15 observations would be 92.

see the attachment for explanation

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