How long did it take for us to get the library card? It only took 15 min; that was fast!

我们 借书证 办了 多长 时间？ = how much time do we need to make a library card? 办了 十五 分钟，办得 真 快。 = (it takes) 15 minutes to make it, (it is) made really fast. textbook 2, unit 16

I would probably say it so: It took us how long to apply for the library card? 15 minutes. That was fast!