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RRB ALP CBT I 26 Nov 2024 Shift 2 Paper

Question : 41 of 75

Marks: +1, -0

The average of the first 30 natural numbers is:

Solution:

Concept:

For the first

n

natural numbers, the average equals

\frac{n+1}{2}

Explanation:

The first 30 natural numbers are

1, 2, 3, \dots, 30

They form an arithmetic sequence with a common difference of

1

The sum of the first

n

natural numbers is

\frac{n(n+1)}{2}

So the average is

\frac{\text{sum}}{n} = \frac{n(n+1)}{2} \div n = \frac{n+1}{2}

Here,

n = 30

Therefore, average

= \frac{30+1}{2} = \frac{31}{2} = 15.5

Answer:

The average of the first 30 natural numbers is

15.5

Hence, the correct option is C.

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