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If Xˉ\bar{X}Xˉ is the mean of x1,x2,x3,…,xnx_1, x_2, x_3, \dots, x_nx1​,x2​,x3​,…,xn​, then for a≠0a \neq 0a=0,  the mean of (ax1,ax2,
Question

If Xˉ\bar{X} is the mean of x1,x2,x3,,xnx_1, x_2, x_3, \dots, x_n, then for a0a \neq 0,  the mean of (ax1,ax2,ax3,,axn(a x_1, a x_2, a x_3, \dots, a x_n, x1a\frac{x_1}{a}, x2a\frac{x_2}{a}, x3a\frac{x_3}{a},....xna\frac{x_n}{a}) is:

A.

(a+1a)Xˉ\left( a + \frac{1}{a} \right) \bar{X}​​

B.

12(a+1a)Xˉ\frac{1}{2} \left( a + \frac{1}{a} \right) \bar{X}​​

C.

(a+1a)Xˉn\left( a + \frac{1}{a} \right) \frac{\bar{X}}{n}​​

D.

(a+1a)Xˉ2n\left( a + \frac{1}{a} \right) \frac{\bar{X}}{2n}​​

Correct option is B

Given:
Let the arithmetic mean of x₁, x₂, x₃, ..., xₙ be X̄ 
Solution:
X̄  = x1+x2+x3+...+xnn\frac {x₁ + x₂ + x₃ + ... + xₙ} n 
x1+x2+x3+...+xn=nXˉx₁ + x₂ + x₃ + ... + xₙ = n \bar{X}​​
 Required Mean=(ax1+ax2++axn)+(x1a+x2a++xna)n+n=a(x1+x2++xn)+1a(x1+x2++xn)2n=(a+1a)(x1+x2++xn)2n=(a+1a)nXˉ2n=(a+1a)Xˉ2\begin{aligned}\text {Required Mean} &= \frac{(ax_1 + ax_2 + \ldots + ax_n) + \left( \frac{x_1}{a} + \frac{x_2}{a} + \ldots + \frac{x_n}{a} \right)}{n + n} \\[6pt]&= \frac{a(x_1 + x_2 + \ldots + x_n) + \frac{1}{a}(x_1 + x_2 + \ldots + x_n)}{2n} \\[6pt]&= \frac{(a + \frac{1}{a})(x_1 + x_2 + \ldots + x_n)}{2n} \\[6pt]&= \frac{(a + \frac{1}{a}) n \bar{X}}{2n} \\&= \frac{(a + \frac{1}{a}) \bar{X}}{2} \\\end{aligned}​​

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