Question

The mean of the observations x, 2x+1, 2x+5 and 2x+9 is 30.What is the mean of first three observations?

Answer 1

Hi ,

Mean of x , 2x +1 , 2x+5 , 2x + 9 is 30

( x+2x+1 +2x + 5 + 2x + 9 )/4 = 30

7x + 15 = 120

7x = 120- 15

7x = 105

x = 105 / 7

x = 15

Now ,

Mean of first 3 terms

= ( x + 2x + 1 + 2x + 5 ) /3

= ( 5x + 6 ) /3

= ( 5 × 15 + 6 ) /3

= ( 75 + 6 ) /3

= 81/3

= 27

Therefore ,

Required mean = 27

I hope this helps you.

:)

Answer 2

Answer:

27

Step-by-step explanation:

x+2x+1+2x+5+2x+9 / 4 = 30

7x+15 / 4 =30

7x+15=30*4

7x+15=120

7x=105

x=105/7=15

mean of first 3 observation --

x+2x+1+2x+5 / 3 =5x+6 / 3

=5 (15) + 6 /3 =75+6 / 3 =81/3 =27