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.

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

Which word is least like the others? Third, fourth, fifth, sixth, seventh, eighth, ninth?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

There’s a girl who has a large family. She has an equal amount of brothers and sisters, but each brother only has half as many brothers and sisters. What’s the correct amount of brothers and sisters?

A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?

While going to your grandmother's house, you counted Twenty houses on the right side. While returning back to your home, you counted Twenty houses on the left side.

How many houses are there between your home and your grandmother's home?

Decode below rebus
D
N
A
T
S , D

Can you name an animal whose killing cannot be performed without spilling your own blood?