Questions

- Send the box with the lock to Alex. 

- Alex can't open it, but can put another lock on the box. 

- Alex sends this box with the 2 locks back to you, you unlock your lock and send it back to Alex again.

- So there is just Alex's lock on the box and Alex can now open it.

The planet Jupiter is known as "Bright Wandering Star".

In the history, Rurik was believed to be the first ruler to consolidate the slavic tribes. He was a Russian leader in the 9th century.

ddNTPs - Dideoxynucleotides and abbreviated as ddNTPs.

They are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing.

They have a hydrogen at the 3’ carbon of the ribose sugar.

Dry ice is solid form of carbon dioxide, used as a cooling agent.

It lower temperature than that of water ice and not leave any residue.

Our solution:

Toss the coin twice.
Let TH, HT and TT correspond to the three choices.
And if you get HH, just repeat (so it takes 8/3 tosses on average).


BIASED COIN

If the coin was biased, TH and HT would occur with equal probability.
So you could assign THHT, HTTH and THTH to the three choices, with other 4-toss outcomes rejected.
Or you could assign HTT, THT and TTH to the three choices, with other 3-toss outcomes rejected.