Catch the Thief

There are 13 caves arranged in a circle. There is a
thief hiding in one of the caves. Each day the the thief
can move to any one of of the caves that is adjacent to the
cave in which he was staying the previous day. And each day,
you are allowed to enter any two caves of your choice.
What is the maximum number of days in which you can
catch the thief?

Age puzzle

The average age of 10 members of a committee is the same
as it was 4 years ago, because an old member has been
replaced by a young member. Find how much younger is
he new member ?

Microsofts Interview Question

There is a table on which a number of coins are placed. You also
know that there are as many coins with Head up as many coins with
Tail up. Now you have to divide the coins (number of coins is even)
into two equal piles such that number of coins with Heads up and
Tails up in either piles be the same. The catch is you are
blind folded and you cannot determine the sides (for sure)
if you are blinded

Optical Illusions

Calender Problem

Syam showed up for work on Monday only to discover that
his delivery truck was in the shop for maintenance. He
was told it would be ready two days after the day before
the day after tomorrow. On what day can Syam expect the
truck to be back on the road?