You have two identical roop. Both of them have the following properties: 1. Each burns in one hour. 2. They burn at a non-uniform rate. i.e. there is

You have two identical roop. Both of them have the following properties:
1. Each burns in one hour.
2. They burn at a non-uniform rate. i.e. there is no correlation between the length of the rope with the time it takes to burn it.
Using only these roops find out when 1.5 hrs have elapsed?
burn rope at both the end simultaneously. It’ll burn in 30 mins. when the first rope completes Then burn the other rope at one end.it ll burn in 1 hour making a total of 1.5 hrs
same two rope how to get 15 mins
first rope burns two end, the second rope burns one end, if first rope finished, stop the second rope.
Then you burn two end of second rope you can get 15 mins