Question

The mean of x, x + 3, x + 5, x + 7, x + 10 is 9. What is the mean of the first 3 observations?

• A. 7.3
• B. 6.67
• C. 7.8
• D. 7

Answer 1

Answer:

B. 6.67

Sum of observations = x + (x + 3) + (x + 5) + (x + 7) + (x + 10) = 5x + 25 , Mean = (5x + 25) / 5 = 9 , 5x + 25 = 45 5x = 20 x = 4 First three observations: 4, 7, 9, Mean = (4 + 7 + 9)/3 = 20/3 = 6.67