I have tried some experiments. Opening 5 new screens, and placing some images there (movie posters) 4 on each screen, the same images, then saving, here are the results:

#1 - PowerPoint Slide Show .ppsx --- size: 553 KB
#2 - PowerPoint 97-2004 Slide Show .pps --- size: 639 KB
#3 - PowerPoint 97-2004 presentation .ppt --- size: 635 KB
#4 - PP Macro-Enabled Presentation .pptm --- size: 553 KB
#5 - PowerPoint presentation .pptx --- size: 553 KB

I can see which is the larger, and so forth -- seems #1 & #5 are the less, not sure what #4 is all about.

THEN I NOTICED SOMETHING FROM MY SOURCE -- is this important?

When I right click on multiple images from the web source, I have choices of which to use. I noticed possible size difference. One image from different sources:

580 X 898
300 X 300
340 X 475
344 X 500
200 X 281

I checked several more images and found the same thing, different stats.

Is this part of my problem as well??? Maybe without looking on Thur and Fri, I took images that were larger and after 110 images, that increased the size as well???

Thanks, Roger