**Question:** Write a program to find the sum of the first `n`

natural numbers.

**Example Input:**`n = 5`

**Example Output:**`15`

**Solution:**

```
n = 5
sum = 0
for i in range(1, n + 1):
sum += i
print(sum)
```

**Explanation:**The loop iterates from 1 to`n`

, adding each number to`sum`

.

**Question:** Write a program to find the factorial of a number `n`

.

**Example Input:**`n = 4`

**Example Output:**`24`

**Solution:**

```
n = 4
factorial = 1
for i in range(1, n + 1):
factorial *= i
print(factorial)
```

**Explanation:**The loop multiplies`factorial`

by each number from 1 to`n`

.

**Question:** Write a program to print the multiplication table of a number `n`

.

**Example Input:**`n = 3`

**Example Output:**`3 x 1 = 3 3 x 2 = 6 3 x 3 = 9 ... 3 x 10 = 30`

**Solution:**

```
n = 3
for i in range(1, 11):
print(f"{n} x {i} = {n * i}")
```

**Explanation:**The loop prints the product of`n`

and each number from 1 to 10.

**Question:** Write a program to reverse a given string.

**Example Input:**`s = "hello"`

**Example Output:**`olleh`

**Solution:**

```
s = "hello"
reversed_s = ""
for char in s:
reversed_s = char + reversed_s
print(reversed_s)
```

**Explanation:**The loop prepends each character of`s`

to`reversed_s`

.

**Question:** Write a program to count the number of digits in a number `n`

.

**Example Input:**`n = 12345`

**Example Output:**`5`

**Solution:**

```
n = 12345
count = 0
while n != 0:
n //= 10
count += 1
print(count)
```

**Explanation:**The loop divides`n`

by 10 until`n`

becomes 0, counting the divisions.

**Question:** Write a program to print the first `n`

terms of the Fibonacci sequence.

**Example Input:**`n = 5`

**Example Output:**`0 1 1 2 3`

**Solution:**

```
n = 5
a, b = 0, 1
for _ in range(n):
print(a, end=" ")
a, b = b, a + b
```

**Explanation:**The loop prints`a`

and updates`a`

and`b`

to the next Fibonacci numbers.

**Question:** Write a program to find the sum of digits of a number `n`

.

**Example Input:**`n = 123`

**Example Output:**`6`

**Solution:**

```
n = 123
sum = 0
while n > 0:
sum += n % 10
n //= 10
print(sum)
```

**Explanation:**The loop extracts the last digit of`n`

and adds it to`sum`

.

**Question:** Write a program to check if a given string is a palindrome.

**Example Input:**`s = "racecar"`

**Example Output:**`True`

**Solution:**

```
s = "racecar"
is_palindrome = True
for i in range(len(s) // 2):
if s[i] != s[-(i + 1)]:
is_palindrome = False
break
print(is_palindrome)
```

**Explanation:**The loop compares characters from the start and end of the string.

**Question:** Write a program to find the largest number in a list.

**Example Input:**`lst = [3, 1, 4, 1, 5, 9]`

**Example Output:**`9`

**Solution:**

```
lst = [3, 1, 4, 1, 5, 9]
largest = lst[0]
for num in lst:
if num > largest:
largest = num
print(largest)
```

**Explanation:**The loop updates`largest`

if it finds a larger number in`lst`

.

**Question:** Write a program to find the second largest number in a list.

**Example Input:**`lst = [3, 1, 4, 1, 5, 9]`

**Example Output:**`5`

**Solution:**

```
lst = [3, 1, 4, 1, 5, 9]
largest = second_largest = float('-inf')
for num in lst:
if num > largest:
second_largest = largest
largest = num
elif num > second_largest and num != largest:
second_largest = num
print(second_largest)
```

**Explanation:**The loop updates`largest`

and`second_largest`

appropriately.

**Question:** Write a program to count the number of vowels in a given string.

**Example Input:**`s = "hello"`

**Example Output:**`2`

**Solution:**

```
s = "hello"
vowels = "aeiou"
count = 0
for char in s:
if char in vowels:
count += 1
print(count)
```

**Explanation:**The loop checks if each character is a vowel and increments`count`

.

**Question:** Write a program to find the sum of even numbers from 1 to `n`

.

**Example Input:**`n = 10`

**Example Output:**`30`

**Solution:**

```
n = 10
sum = 0
for i in range(2, n + 1, 2):
sum += i
print(sum)
```

**Explanation:**The loop iterates over even numbers and adds them to`sum`

.

**Question:** Write a program to count the number of words in a given string.

**Example Input:**`s = "hello world"`

**Example Output:**`2`

**Solution:**

```
s = "hello world"
count = 1
for char in s:
if char == ' ':
count += 1
print(count)
```

**Explanation:**The loop counts spaces and adds 1 to get the number of words.