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RRB NTPC Prelims Model Paper 2 with solutions

Question : 7 of 101

Marks: +1, -0

The average of first thirty natural numbers is

Solution:

Concept:

The average of the first

n

natural numbers is their total sum divided by

n

Explanation:

Sum of first

30

natural numbers is

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

Put

n = 30

S = \frac{30 \times 31}{2}

S = 15 \times 31 = 465

Average

= \frac{S}{n} = \frac{465}{30}

Thus average

= 15.5

Answer:

The average of the first thirty natural numbers is

15.5

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