I am not tech savvy. But I like to solve quiz relates math and physics. I was solving such questions and come across this question. "On a cloudy day, a sealed packet of potato chips is taken to the top of a mountain. The packet is found to be blown up like a balloon." What is the reason behind it? I found two reasons as per my knowledge, 1. The air outside the packet is hotter than the air inside the packet or 2. The air outside is now at a lower pressure than the air inside the packet. Which one is the right reason? Please guide me in detail.