As long as you need it to be! There is no magic formula to determine length on a persuasive writing - use as many words as you need to properly convince your readers that your opinion is the right one!
About five sentences.
A good persuasive letter should have a clear and compelling argument, with supporting evidence and examples. It should also be written in a persuasive tone, using language that is engaging and convincing to the reader. Additionally, it should address the reader's concerns and provide a call to action.
A persuasive letter to your local administration for more facilities for young people should be signed by the person who writes it.
well find out what a persuasive b lain letter is first and go from there
Persuasive memos and memos that communicate bad news should be written in formal style. If the memo gets lengthy change the format to a letter.
A persuasive letter should begin with a strong and engaging opening statement to capture the reader's attention. This could include a bold statement, a compelling question, a relevant statistic, or a personal anecdote. The goal is to pique the reader's interest and establish the purpose of the letter right from the start.
A persuasive email is a letter where the writer tries to convince the reader to do something.
Long enough to state your main theme: your argument. Then, no more that two or three average sized paragraphs to tell why you believe as you do, then a good summation of your reason for the persuasion which re-states your belief. Brevity is better than rambling.
A letter requesting support should be polite but persuasive. The writer should make assertions, then follow them up with supporting evidence.
It depends on how you present it; if you want it to be persuasive it has to be persuasive about something, like you should donate to charity or people should not act as if poor people do not exist etc. But if you are simply informing people about poverty it wouldn't be considered persuasive.
A letter to someone of importance trying to "persuade" them of a proposed idea.
Persuasive communication is any form of written, verbal communication, wherein the communicator (speaker/writer) is trying to convince the listener/reader to his way of thinking. Any sales presentation, business letter, sales letter is an example of persuasive communication.