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.
justpuzzles 
(solution removed)
iitian,
I welcome your contributions. Additions, variations, solution times: they are all appreciated.
But please dont spoil the fun for others by posting the answers. For that reason I will removes this remark.
Cool Sir will not put my solution comment!!..It was done only b’cos I just did not see the solution link and did not know your policy of publishing the answer after 1-2 weeks.
Thanks for your efforts 🙂
Iitian,
I’m glad you don’t take my remark personally. I highly appreciate your often very constructive remarks.