Question

If mean of five observations x + 1, x + 2 , x + 3, x + 4 and x + 5 is 15, then mean of first three observations is​

Answer 1

Answer:

4

Explanation:

We know that,

$Mean = \frac{sum \: of \: observatins}{total \: number \: of \: observations}$

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

$\frac{5x + 15}{5} = 15$

.

$5x + 15 = 75$

$5x = 75 - 15$

$5x = 60$

$x = \frac{60}{5}$

$\boxed{x = 2}$

Now according to the question, mean of first three terms. Putting x = 2

$Mean = \frac{x + 1 + x + 2 + x + 3}{3}$

$\frac{3x + 6}{3}$

$\frac{3(2) + 6}{3}$

$\frac{6 + 6}{3}$

$\frac{12}{3}$

$\boxed{Mean = 4}$

Hence the mean of first three terms is 4