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

Solution(By Examveda Team)

Let the four observations are = a, b, d, e
According to the question,
$$\frac{a + b + e + d}{4}$$   = 20.....(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