Question

If the mean of four observations is 20 and when a constant c is added to each observation, the mean becomes 22. The value of c is :

• A. -2
• B. 2
• C. 4
• D. 6

Answer 1

Answer: (B)

Mean of four observations = $20$
$\therefore$ total observations = $20\times 4=80$
When add c in each observation total observation will be $80+4c$, then new mean = $22$
$\therefore$ According to the question,
$80+4c=22\times 4$
$\Rightarrow 80+4c=88$
$\Rightarrow 4c=8\Rightarrow c=2$