he was asked to work out 13,852 x 1/8 off the top of his head?
When I first read that part of the original post my first reaction was along the lines of..."and just how many People could actually work that out in their heads??"
I used to top the Class in Primary School in Mental Arithmetic (mid to late 60's) when it was a fundamental part of Schooling in South Australian Primary Schools.
I'd struggle to even begin to calculate that sort of problem now!
OK fellow Ppruners; Be honest now! Whom amongst us could do that calculation?