In the program below, we've used an if...else statement in combination with a while loop to calculate the sum of natural numbers up to num.
Source Code
# Sum of natural numbers up to num
num = 16
if num < 0:
print("Enter a positive number")
else:
sum = 0
# use while loop to iterate until zero
while(num > 0):
sum += num
num -= 1
print("The sum is", sum)
Output
The sum is 136
Note: To test the program for a different number, change the value of num.
Initially, the sum is initialized to 0. And, the number is stored in variable num.
Then, we used the while loop to iterate until num becomes zero. In each iteration of the loop, we have added the num to sum and the value of num is decreased by 1.
We could have solved the above problem without using a loop by using the following formula.
n*(n+1)/2
For example, if n = 16, the sum would be (16*17)/2 = 136.
Your turn: Modify the above program to find the sum of natural numbers using the formula below.
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