Ezra: Mommy, is the cake ready?
Me: It's done baking, but now it needs to cool.
Ezra: How many seconds will it take to cool?
Me: I don't know, maybe 15 minutes or so.
Ezra: How many seconds?
Me: Maybe...900 seconds.
Ezra: 900. 1, 2, 3, 4, 5, ....