When can we add 2 to 11 and get 1 as the correct answer?

Can you replace the question mark with the correct number in the below table sequence?

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

What is the Surname of Barbie Doll?

At the local model boat club, four friends were talking about their boats.

There were a total of eight boats, two in each colour, red, green, blue and yellow. Each friend owned two boats. No friend had two boats of the same colour.

Alan didn't have a yellow boat. Brian didn't have a red boat but did have a green one. One of the friends had a yellow boat and a blue boat and another friend had a green boat and a blue boat. Charles had a yellow boat. Darren had a blue boat, but didn't have a green one.

Can you work out which friend had which coloured boats?

What does this mathematical rebus means ?

Why did Navjot Singh Sidhu put the new January calendar in the freezer

What has a ring but no finger?

Buy me, smell me or deliver me, I do not change.

Who am I?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?