Question

From a series of $50$ observations, an observation with value $45$ is dropped, but the mean remains the same. What was the mean of $50$ observations?

• A. $50$
• B. $49$
• C. $45$
• D. $40$

Answer 1

The correct option is C $45$

Let no be $a_1,a_2....a_{49}$

then $\frac{a_1+a_2+..+a_{49}}{49}=45$

if we add '45' also

then $\frac{a_1+a_2+a_{49}+45}{50}$

$=\left(\frac{49\times 45+45}{50}\right)=45$