Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

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?

Chocolate costs 6 rupees and a Toy costs 5 rupees. If you have 32 rupees in total, how many chocolates and how many Toys can be purchased with that amount?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

A man is found hanging dead from the ceiling of a room. The room’s dimensions are 15 x 15 x 15. The man is only 6ft tall and the rope was only 2ft long. There are no windows and only one door to the room. The door is bolted shut from the inside, and a puddle of water is under the man. How did he kill himself?

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

Forwards I am heavy, backward I am not. What am I?

What has no start, end, or centre?

What Time Should the last watch show in the below figure?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?