Puzzles!

Here are two interesting puzzles taken from the book 'How Many Socks Make a Pair' by Rob Eastaway. (Well the didn’t make up the puzzles himself though, so u can find the same puzzles elsewhere too)

The Burning String
You are given only a piece of rope and a lighter, and you have no other way to tell the time/keep track of them. The rope burns for exactly one hour, how do you tell if 30 minutes have passed? Cutting the rope into two wont work though, since the rope is of unequal thickness and each part takes and unequal amount of time to burn...


Where is the Father?
A women is 21 years older than her son. In six years time, she will be five times as old as her son. Where is the father?




Answers
The Burning String
Start burning the rope from BOTH ends. When entire rope burns to ashes you have 30minutes!

Where is the Father?
It seems like the question is completely unrelated to the clues given... but do some simple algebra (which i am too lazy to write) and you will find that the sons age is -3/4... which is around the time of conception aka the child is 9months away from being born... so where is the father haha?