If the mean of 4 observations is 20, when a constant ‘c’ is added to each observation, the mean becomes 22. The value of c is :
A. 6
B. −2
C. 2
D. 4
Answer: Option C
Show Answer
Let the four observations are = a, b, d, e
$\begin{array}{l}\text{According to the question,}\\
\frac{a+b+e+d}{4}=20\ldots..\text{ (i) }\\
\frac{a+c+b+c+e+c+d+c}{4}=22\\
\frac{4c+(a+b+e+d)}{4}=22\\
\frac{4c}{4}+20=22\\
c=2\end{array}$
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