# Data Structure Questions and Answers-Sum of n Natural Numbers using Recursion

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 Question 1
Which of the following methods can be used to find the sum of first n natural numbers?
 A Iteration B Recursion C Binomial coefficient D All of the mentioned
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Question 1 Explanation:
All of the above mentioned methods can be used to find the sum of first n natural numbers.

 Question 2
Which of the following gives the sum of the first n natural numbers?
 A nC2 B (n-1)C2 C (n+1)C2 D none of the mentioned
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Question 2 Explanation:
The sum of first n natural numbers is given by n*(n+1)/2, which is equal to (n+1)C2.

 Question 3
Consider the following iterative solution to find the sum of first n natural numbers:

#include<stdio.h> int get....sum(int n) { int sm = 0,  i; for(i = 1; i <= n; i++) .....; return sm; } int main() { int n = 10; int ans = get....sum(n); printf("%d", ans); return 0; }

Which of the following lines completes the above code?

 A sm = i B sm += i C i = sm D i += sm

Question 3 Explanation:
The line "sm += i" completes the above code.

 Question 4
What is the output of the following code?

#include<stdio.h> int get....sum(int n) { int sm,  i; for(i = 1; i <= n; i++) sm += i; return sm; } int main() { int n = 10; int ans = get....sum(n); printf("%d", ans); return 0; }
 A 55 B 45 C 35 D none of the mentioned
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Question 4 Explanation:
Since the variable "sm" is not initialized to 0, it will produce a garbage value.

 Question 5
What is the time complexity of the above iterative method used to find the sum of the first n natural numbers?
 A O(1) B O(n) C O(n2) D O(n3)
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Question 5 Explanation:
The time complexity of the above iterative method used to find the sum of first n natural numbers is O(n).

There are 5 questions to complete.