If eleven plus two equals one, what does nine plus five equal?

The following sentence is false. The preceding sentence is true.
Are these two sentences true or false?

A girl says this to her best friend: “I was born in 1955, and I celebrated my 17th birthday last weekend.” Her best friend thinks she’s lying, but she’s actually correct. How is that possible?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

Teacher ask the student

'Why are you standing on that chair in music class ?'.

what did student replied ?

Two guards were guarding the camp.Guard-1 was looking towards the south to make sure no threat is coming from the road.Guard-2 was looking at the north to make sure no threat is coming from the top. Suddenly Guard-1 ask the Guard-2 why he is smiling?How Guard-1 knows that Guard-2 is smiling?

Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

Christina makes tasty toast in a small pan. After toasting one side of a slice, she turns it over. Each side takes 30 seconds. The pan can only hold two slices.
How can she toast both sides of three slices in 1 & 1/2 instead of 2 minutes?

Find the missing number in the image below.

When is the top of a mountain similar to a savings account?