You have a fox, a chicken, and a bag of chicken feed, and must take them all to the other side of a river. You have a boat but can only take one thing across at a time. You cannot leave the chicken with the fox, nor the chicken with the bag of chicken feed. How will you get them all across??
First, you must take the chicken aross. Then bring the chicken feed, but while on the other side grab the chicken and take it back across. Next, leave it on the first side and take the fox across. Last bring the chicken.