Using four times the number four, create the number 81. You may use the usual mathematical operands.
If you are puzzled, we have a solution for you.
I would like to thank Kees Krol again for coming up with this one.
As always, please don’t publish your solutions. Solutions can be found after 1-2 weeks on the solution page for those who want to check their solutions, or for those who are really stuck.
But scrolling is much easier, and really spoils the fun for others.