这个题目取自project Euler, Project Euler是一些可以通过巧妙(有时也不是很巧妙)的计算机编程解决的数学题集。

This problem is taken from Project Euler, a collection of mathematical problems that can be solved using clever (or sometimes not-so-clever) computer programming.

youdao

每一次更换的题目大概是淘30%到40%的旧题，并且补充相应数量的新题，每一次在换题完成之后，题库就会相对的比较的稳定直到下一次的换题时间。

There are 30% to 40% old questions each change and there are some amounts of makeup. After each change, it will be the new time of change.

youdao

下面给个直截了当的例子，请做好心理准备作业里，可能会遇到这种题，或者说，各位如果三生有幸，考试中也会，出现类似的题目。

Let's do a straightforward example the way that you could expect it on an assignment or, if you were extraordinarily lucky you might even get something like that on an exam.

youdao

When you go today and look at the homework, you'll find the problem from the textbook, one extra problem that deals with all of this.

你们今天回去看到作业,就会看到课本上的一道题目,这道附加题涵盖了所有知识点

耶鲁公开课 - 基础物理课程节选

So the problem I want to do-- there are many things you could do but I just picked one, and this is the one with round numbers, so I can do it without a calculator.

我想讲的这道题,类似的题目很多,但我就选了其中一个,这道题涉及的数字都是整数,所以我不需要计算器

耶鲁公开课 - 基础物理课程节选