I travel all around the world but always stay in the corner. What am I?

What runs around the whole yard without moving?

Can you find the key in the picture below?

Solve below rebus puzzle?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

A train leaves from point A for point B at 80 mph. After half an hour, another train leaves from point B for point A at 60 mph.

Which of the trains will be farther from point A when they meet ?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?