The arithmetic mean of first 11 natural numbers is · ABC26GN1536

Subject: General Aptitude · Chapter: Average · Exam: P.C.S. 2009

The arithmetic mean of first 11 natural numbers is

(a)5

(b)5.5

(c)6.0

(d)6.5

Answer

Answer (as printed): C

Explanation

Required mean $=\left(\frac{1+2+\cdots+11}{11}\right)=\left(\frac{1}{11} \times \frac{11 \times 12}{2}\right)=6$. $$\left[\because 1+2+\cdots+n=\frac{n(n+1)}{2}\right]$$

Explanation as extracted from the printed page; notation may be imperfect.

Study loop for Average

1. Practise the PYQsPrevious-year questions, with answers

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