In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.

Example Input: Sentence: 'a man being towed behind a boat on a board'. Reverse all words of length '4' in the given sentence.
Example Output: a man being towed behind a taob on a board

Example Input: Sentence: 'young skateboarder on paved roadway near grassy slope'. Reverse all words of length '6' in the given sentence.
Example Output: young skateboarder on paved roadway near yssarg slope

Example Input: Sentence: 'a man flying through the air on top of a skateboard'. Reverse all words of length '7' in the given sentence.
Example Output:
a man flying hguorht the air on top of a skateboard