To adjust the speed of a slide, click on the slide in the slideshow, then open the Animations tab. Choose the Speed effect from the Effects Library.
Enter a percentage into the box (or drag the trackbar) to update your slide with the new speed.
100% is the original speed of the slide. To slow your slide down, enter a lower percentage. To speed it up, enter a higher percentage. Some example values are:
Playing Video Backwards
To play video backwards, select the Play slide backwards radio button option in the Speed Change effect. You can also adjust the speed if desired.
To remove the speed effects, click the white cross delete button on the top-right of the Speed Change item in the Effects applied to this slide list. The slide will return to the original speed and playback direction (forwards).