Instead, I'm going to set a very simple mathematical problem based on something I saw pointed out last week, I will credit where I saw it but not yet as that kind of ruins the effect. It's really simple maths, or as americans would say "math", I assume they dropped the 's' to make it available for referring to Lego as "Legos"...
You have to crack a combination lock with a 7 dials, each dial can be turned to ten positions, showing the digits 0-9, the only slightly weird thing about the lock is that each digit can occur only once in the correct combination.
You can try one combination per second.
How long will it take to try all valid combinations?
Give the answer in weeks, days, hours, minutes & seconds
(don't scroll down if you want to work it out, this is just padding
in case anyone is actually interested enough
to post the answer in the comments)