It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

A man dies of old age on his 25 birthday. How is this possible?

Can you find out the number of the parking space in which the car is parked?

What is wrong in the below Picture?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Kareena is older than Katrina and younger than Karishma. Isabelle is younger than Bipasha and Karishma. Bipasha is older than Karishma. If Kareena and Isabelle are the same age, who's the youngest?

What is the next number in this matchsticks series riddle?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?