Question

The mean of $11$ observations is $50$. If the mean of first six observations is $49$ and that of last six observations is $52$, which option is the sixth observation?

• A. $55$
• B. $56$
• C. $57$
• D. $58$

Answer 1

Answer: (B)

$56$

Mean of $11$ observations $=50$

Mean of first $6$ $=49$

Last $6$ $=52$

Total sum of observation $=50\times 11=550$

Total observation of first $6$ $=49\times 6=294$

Total observation of last $6$ $=52\times 6=312$

Sixth observation $=294+312-550=606-550=56$