10. 1 ft analysis: the key to solving this problem is to understand the meaning of the problem, understand the difference between ancient languages and modern languages, and turn the problem into Pythagorean theorem to solve it.

Answer: Let the width of a single door be x meters. According to Pythagorean Theorem, it is x2= 1+(x-0. 1)2, and x=5.5, then 2x= 10. 1 foot.

Comments: The difficulty of this question is to understand the meaning of the question, find the right triangle, calculate according to Pythagorean theorem, and copy the translation result from Google Translation.