Joke of the year

As you know from the ongoing War On Innumeracy, I am a maths nerd (or, as they say in the US, a "math nerd"). I have a friend who is also a maths nerd. We had a conversation the other day which I thought was not only incredibly nerdy, but also very funny. If you aren't nerdy enough to understand it, I'll explain it at the end.

Friend (serious)
I don't know how my mum cooks for (say) 20 people. I'm flustered enough cooking for 4.

PTR (smart-arse)
The secret to cooking for 20 is to cook for 19 people and dish up slightly smaller serves. In fact this works for all N>1.

Friend (seizing the moment)
Ah, so that's what an induction cooktop is.

Joke's over folks. You see, induction can refer to a mathematical proof whereby it is shown that if a statement is true for N, then it is also true for N+1, and thus since it is true for some known value of N, it is therefore true for all greater values. And an induction cooktop uses the mystical power of electromagnetism to create eddy currents within a metallic pot which heats it to cooking temperatures.

Pretty funny, huh?