"What's 251 times 864?"
And I thought about this and I said "216864". Because it was a really easy sum because you just multiply 864x1000 which is 864,000. Then you devide it by 4, which is 216,000 and that's 250x864. Then you just add another 864 onto it to get 251x864. And that's 216,864.

Quoted from "The Curious Incident of the Dog in the Night-Time". A novel by Mark Haddon.