On one hand, I liken easy busy work to crawling after you know how to walk. It's pointless and demeaning.
On the other hand, I liken easy busy work to washing the dishes. Smart people have to do chores, too. Perhaps you can focus on the idea that accomplishing menial tasks efficiently is an important skill to develop.
Alternatively, your son could try and make the best out of the situation. He could test himself to see how many ways he can come up with to accomplish the tasks at hand. For some problems, he could start with the least significant digits, while starting with the most significant digits on other problems. Play around with it. My dad used to tell me story of a young child who was asked to add up all the numbers from 1 to 100. Instead of adding them, the student came up with the formula for calculating the sum of any arithmetic series, and applied it.
Also, don't forget to be thankful for what you have. Being bored for a few weeks is much preferable to being bored for several years.
