Question

If the mean of 5 observation x+1, x+2, x+3, x+4 and x+5 is 15, then what is the mean of first 3 observations?

• A. 14
• B. 15
• C. 16
• D. 10

Answer 1

Answer:

A. 14

$\frac{x+1+x+2+x+3+x+4+x+5}{5}=15$

$\frac{5x15}{5}=15$

$5x+15=15\times 5$

$x=\frac{75-15}{5}$

$x=12$

$x+1=12+1=13$

$13, 14, 15$

$=14$