Question

Q.20. If the mean of first n natural number is 15, then find n.
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Answer 1

Answer:

29

Step-by-step explanation:

The first n natural numbers are 1,2,3,...,n

Given that mean of n natural numbers is 15

⟹n1+2+3+...+n=15 ———(1)

We know that sum of first n natural numbers is 2n(n+1)

⟹1+2+3+...+n=2n(n+1) ———(2)

Substituting (2) in (1) we get

⟹2nn(n+1)=15

⟹n+1=30⟹n=30−1=29

Answer 2

Answer:

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