Brad DeLong's Request for help

My two children get what the payoff to reading well is immediately and completely. My two children get what the payoff to writing well is as well: they understand that it is fun now and it will be important later on if they want to have options to be able to write quickly, clearly, and coherently.

But math. Math textbooks are remarkably dry. How can I persuade them that math can be fun, that they will be able to learn and calculate interesting things if math is their friend, and that their options later on will be much, much greater if only they apply themselves to math now?

So far, I only have twenty-three problems that I regard as interesting and amusing enough to hand them in an attempt to propagandize for math. But I want more: I want to have one hundred…

Have a look at Brad DeLong's Collaborative Website: OneHundredInterestingMathCalculations.

When I was a child, and very much into the space program and science fiction, I found it very entertaining to calculate the delta-V for various interplanetary journies. (For simplicity’s sake I assumed all the planets were in the same plane.) It’s quite easy to do, starting from basic physical laws. You need algebra, but no calculus, and a table of the masses and orbital radii of the various planets, and of the sun.