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Cotton's non-wicking properties are part of it. The other part of it is the only reason to be wearing clothing while hiking is for insulation. Dry cotton works well for this purpose. Wet cotton is no longer insulative. Wet synthetics do not lose their insulative properties to nearly the same degree, and they dry MUCH faster. If you're hiking in jeans, a tee shirt, and a cotton sweatshirt in 40 degree weather and get hit with a freak thunderstorm, you are in serious trouble. If you're hiking in all synthetic clothing, just keep moving. You might get uncomfortable, but you won't get hypothermia. Polypropylene is good, capilene long underwear makes a great thermal layer, synthetic fleece is okay, nylon is fine. Even wool has its uses. I knew one guy who hikes in 100% polyester work shirts. Don't carry cotton.

I was a thru-hiker in 2000 and did a 100 mile section about a month ago, in addition to a 170 mile section before my thru-hike. The Smokies and the Shenandoahs are both great places to do a week section. Vermont is gorgeous if you've got a couple or three weeks. You'll need a pack. Get a good pack. I use a Gregory Z55 for summer trips. You'll need a sleeping bag - what kind depends on where and when you're going. You'll need a water filter. I use a katadyn hiker. You'll need a stove. The gas cannister stoves are the easiest if you're a beginner. Leki poles are a must if you value your knees. I really prefer trail running shoes over boots for summer travel. Again, easier on your joints. The typical beginner mistake is to overpack, but that's something you'll learn by experience. Cotton kills. Nothing in your pack should be cotton. Not clothes and not equipment. Not even underwear.

He's taking five real college level math classes, which will take two years to get through. You've gotta assume that he's in an engineering or science track, as that's way too much math for any humanities program. Its worth spending the $150, even if it means eating ramen for a month. Of those choices, though, the 86 is much better suited. The 83 is really designed for late middle school to mid high school. Its not even going to be any real help in calc 1.

TI-89. hands down. The 83 is a toy, and the 86 is archaic. The 89 has the best games, too, for what that's worth.

I'm completely new here, but know a thing or three about backpacking. I personally carrying the following for first aid on week-long or shorter trips: 50 ibuprofen 6 inches of duct tape If anything hurts, take the ibuprofen. If anything is red/blistered/burned/bleeding, put duct tape on it. I'm running a 10 pound summer core weight (everything except food and water, including pack), though. What's your level of backpacking experience? For short trips you can't beat the mountain house meals. That, three pounds of snickers bars and a tub of gatorade should get you through.