One of my classrooms doesn't have a projector system. It has a computer, and a screen, but no projector. However, I can check out a portable projector from the library, and since we had videos to watch today, I did.
So I got to the classroom early and got the projector set up, and made sure it was projecting, and we got through the bits that didn't require sound. Then we fired up the videos... no sound. I unmuted the computer... no sound. I tried turning up the volume with the remote, and the remote didn't work. I figured out how to adjust the volume from the buttons on the projector... no sound. I went back to the remote, thinking maybe the projector was muted - and discovered the remote didn't have batteries.
So I walked around the floor, seeing if there was an empty room with a projector system whose remote I could gank (hah, I'm funny). I went back to my room, and tried to find "mute" in the menu on the projector. However, the menu was in French.
At that point, I threw up my hands, I told them what would have been in the videos, and they left early.
As I was packing up the projector and folding up the cords, what do I find in the front pocket? The batteries.