how to make words appear letter by letter in a presentation

i want to make words appear one letter at a time in my presentation. how do i do that?

Click in the text box you want to use the effect. Open the sidebar if it is not already (menu option: View->Sidebar). Click on the Animation button to open the Animation sidebar.

Add the animation Category: Entrance, Appear.

Right click on the list of animations at the top of this sidebar and select: Effect Options…

Under the Effect Tab select: Enhancement, Text animation: Letter by letter. You may need to adjust percent delay between characters to slow the letter appearance down. I had to use 50,000% to get a reasonable delay between letters appearing. It looks like this is related to the Timing tab’s total time for the effect. For example: I set the total time to 1.5 seconds and then 33% delay worked fine…

This will make text appear, letter by letter, until the entire text is on-slide. Feel free to play with the timing options and other selections. There are a lot of ways to adjust this. Have fun.

I had to set 9.000% for a reasonable value; i wonder is that nine thousend % ?
And in the timing tab the duration is gray, not active. I can set only a delay (whis is best 0,0 sec)