a geeky way to disturb your children

A: We can make pyand sometime.
S: What is pyand?
A: No, PI END.
S: (?)
A: It doesn't have to go on forever. We can write the whole thing down.
(Loyal readers may recall that we discussed pi with the children about a month ago. A has voiced frets over it several times since then.)
S: Well, um, in a way you're writing the whole thing every time you draw a circle.
A (thankfully ignoring my last statement): We should make pi end. Let's do that now.
S: Well, usually people shorten it, so we can just decide to stop after three digits and call it 3.14.
A: (displeased)
S: The rest of the numbers after that are so small that they're not very important anyway.
A: Why aren't they important?
S: Because they're so small compared to the first three numbers.
A: But I want it to stop at 9.
S: Oh, so you want it to be 3.14159?
A: Yes!!
S: OK, sounds good.
A: What is it again?
S: 3.14159.
A (after taking a bite of dinner): What is it again?
S: 3.14159.
A: 3.14159?
S: Yes.
A (very pleased): Oh!