Explanation

To find the sum, we add the numbers together:

11

33

55

77

99

Starting from the rightmost digit (ones place):

1 + 3 + 5 + 7 + 9 = 25

Write down 5 and carry over 2 to the next place.

Moving to the next digit (tens place):

1 + 3 + 5 + 7 + 9 = 25

Add the carry-over 2: 25 + 2 = 27

Combine the digits: 275

So, 11 + 33 + 55 + 77 + 99 = 275