Brain Bruisers

Sometimes I like to stretch my mind and contemplate riddles and brain teasers just for the fun of it. Here’s a few that I liked. Let me know what you think might be the answers. I’ll post all the correct answers in a day or two to give people time to work through some possibilities. I hope I’m not the only one who was stumped by these…   

Enjoy!!

1. What's black when you get it, red when you use it, and white when you're all through with it?

2. You throw away the outside and cook the inside. Then you eat the outside and throw away the inside. What did you eat?

3. Three closed boxes have either white marbles, black marbles or both, and they are labeled white, black and both. However, you're told that each of the labels is wrong. You may reach into one of the boxes and pull out only one marble. Which box should you remove a marble from to determine the contents of all three boxes?

4. During WWII, there was a bridge connecting Germany and Switzerland, and on the German side, there was a sentry tower with a guard in it. He would come out every three minutes to check on the bridge, and he had orders to turn back anyone who tried to get into Germany, and shoot anyone trying to escape without a pass. There was a woman who desperately needed to get into Switzerland, and she knew she didn't have time to get a pass. It would take her at least six minutes to cross the bridge, but she managed to do it. How?