Burning Rope/wood puzzle

Question:

I have some number of  non-homogeneous ropes(or woods or fuses), and each one of them needs 1 hr to be burned. Material is non-homogeneous that means if i cut the rope into two equal parts(in the term of length), it is not necessary that both burns in the same time.

(Some may ask about wood(or fuse) instead of rope... but trick is same for solving.)

Q 1.) How can i calculate 45 minutes using those two ropes?!

Q 2.) How can i calculate 15 minutes using only one rope?!

Ans 1:

1. Fire first rope from both side (front side and rear side) and in parallel start fire in the second rope only from one side.(let say front side)
2. When one rope will totally burned, on that time start fire in the second rope from rear part. (one rope will totally burn in 30 minutes because as we have double the speed, time taken would be half. It means as one rope needs 1hr to be burn, by doubling the speed so in 30 mins.)
3. When second rope also totally burn, it would be exactly 45 minutes. (because at the end of 30 minutes, it will burn half part, and after that we have double the speed, so at the end of 15 minutes, second rope also totally burned. So total time is 30 minute + 15 minute = 45 minute.)