Question

if the mean of 5observation are x,x-2,x+4,x-6 and x+8 is 11 find the mean of first 4 observation​

Answer 1

$no. \: of \: observations = 5$

$observations = x,x - 2,x + 4,x - 6,x + 8$

$mean \: of \: five \: obvns. = \frac{x + x - 2 +x + 4 + x - 6 + x + 8}{5}$

$11 = \frac{5x + 4}{5}$

$5x + 4 = 11 \times 5$

$5x = 55 - 4$

$x = \frac{51}{5}$

Then, the observations are,

$\frac{51}{5} , \frac{51}{5} - 2, \frac{51}{5} + 4, \frac{51}{5} - 6, \frac{51}{5} + 8$

$= \frac{51}{5} , \frac{51 - 10}{5} , \frac{51 + 20}{5} , \frac{51 - 30}{5} , \frac{51 + 40}{5}$

$= \frac{51}{5} , \frac{41}{5} , \frac{71}{5} , \frac{21}{5} , \frac{91}{5}$

The mean of first four observations are,

$= \frac{\frac{51}{5} + \frac{41}{5} + \frac{71}{5} + \frac{21}{5}}{4}$

$= \frac{ \frac{51 + 41 + 71 + 21}{5} }{4}$

$= \frac{ \frac{184}{5} }{4}$

$= \frac{184}{5} \times \frac{1}{4}$

$= \frac{46}{5} \: or \: 9.2$

Answer 2

Answer:

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