It is always ahead of me yet I can never see it. What is it?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

What is full of holes but still holds water?

At my favorite fruit stand,
an orange costs 18,
a pineapple costs 27,
and a grape costs 15.
Using the same logic, can you tell how much a mango costs?

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

The current time can be represented by below textual rebus.

0
=========
B.Sc
LLB

Can you tell us the current time?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Replace the question mark in the picture below.

When 99 is considered higher than 100?

That attorney is my brother, testified the accountant.

But the attorney testified he didn't have a brother.

Who is lying?