Fellow speaker,
People tend to talk at about 150 words per minute. At 10-12 words per written sentence, after 15 sentences we have spoken for about a minute. So if you want to do a 10 minute talk, you need to have about 150 sentences in our written speech. Writing the speech out helps makes sure you know the exact length of your talk so you will never run out things to say during your talk.
Writing it out,
Tim
