question_answer

If the mean of five observations x, x + 2, x + 4, x + 6, x + 8, is 11. Find the mean of first three observations,.

Answer:

We have, \[11=\frac{x+(x+2)+(x+4)+(x+6)+(x+8)}{5}\] \[11=\frac{5x+20}{5}\] 55 = 5x + 20 5x = 35 x - 7                                                                                                                                          \[\therefore \]Mean of first three observations \[=\frac{x+(x+2)+(x+4)}{3}=\frac{3x+6}{3}\] \[=x+2=7+2=9\] \[1{}^{1}/{}_{2}\] [\[\because \]x=7]