How can you place the numbers 1 through 9 in a 3×3 grid such that every row, column, and the two diagonals all add up to 15?

How can you place the numbers 1 through 9 in a 3×3 grid such that every row, column, and the two diagonals all add up to 15?

There are 13 caves arranged in a circle. There is a thief hiding in one of the caves. Each day the thief can move to any one of the caves that is adjacent to the cave in which he was staying the previous day. And each day, two cops search any two caves of their choice for the thief. So, one cave is searched per cop per day.

The following conditions apply.
What is the minimum number of days to guarantee in which the cops can catch the thief?
Riddle AnswerThe cat and the rabbit weigh 10kg. The dog and the rabbit weigh 20kg. The dog and the cat weigh 24kg. What is the total weight of the dog, cat and rabbit?

Look at the 9 dots in the image. Draw 4 straight continuous lines without lifting the pen from the paper and make sure that the lines pass through each of the nine dots.
