Question

if the mean of the observations x 2x+1 2x+5 2x+9 is 30 find the mean of last 2 observations

Answer 1

here is your answer hope it helped you

Answer 2

The mean of last 2 observations is 37.

The observations are : x, 2x+1, 2x+5, 2x+9

Total sum of the observations = x + 2x+1 + 2x+5 + 2x+9 = 7x + 15

No. of observants = 4

∴ Average = (Total sum) / (No. of observants)

= (7x + 15)/4

Given, the average is 30. So,

(7x + 15)/4 = 30

⇒ 7x + 15 = (30×4) = 120

⇒ 7x = 120 - 15 = 105

⇒ x = 105/7 = 15

So, the last 2 terms are

1) 2x + 5 = 2(15) + 5 = 35

2) 2x + 9 = 2(15) + 9 = 39

So, average is (35+39)/2 = 74/2 = 37

The average of the last 2 terms is 37.