Question

Question 2: Write a program that input a number from user, calculate the sum of prime
numbers from 1 to number entered by user.
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Answer 1

Answer:

Program to find sum of prime numbers between 1 to n

Write a program to find sum of all prime numbers between 1 to n.

Examples:

Input : 10

Output : 17

Explanation : Primes between 1 to 10 : 2, 3, 5, 7.

Input : 11

Output : 28

Explanation : Primes between 1 to 11 : 2, 3, 5, 7, 11.

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

A simple solution is to traverse all numbers from 1 to n. For every number, check if it is a prime. If yes, add it to result.

An efficient solution is to use Sieve of Eratosthenes to find all prime numbers from till n and then do their sum.