Tricky(?) Crocodile Maths Exam Question

[Thomas Klemm]

(10-09-2015 03:47 PM)Gerald H Wrote:  calculator or pencil & paper?

Using Snell's law we can conclude that we deal with two similar triangles with Pythagorean triples (3, 4, 5) and (6, 8, 10). Thus x = 8 is trivial.
The time needed is: \(5\cdot10+4\cdot12=50+48=98\).
I need neither a calculator nor pencil and paper for this.

Cheers
Thomas

PS: I could understand the reaction if this was one of these hard problems.