My solution is based on assuption that these two ropes are hanging close to each other, so you can reach from one another.
1. Climb up on rope #1 to the seiling.
2. Swing it and grab rope #2.
3. Cut rope #2 just at the ceiling, with your knife.
4. Drop it on the floor.
5. Descend down to the point where is 10 feet left.
6. Cut 10 feet from rope #1.
7. Jump 10 ft to the floor.
8. Now you have 40 + 10 = 50 feet.
9. Tie them together so you will have a 50 ft rope.
10. Attach it somewhere on a top of that wall.
11. Descend on it.
12. Jump from 10 ft height.

[Itzik: if you noticed I mentioned "A few minutes later, you find another 40-foot rope hanging from ceiling to floor." This was a hint that the ropes are not hanging close to each other.]

Mark2/22/2007 3:13:13 PM

I give up

JACOB2/20/2007 1:25:12 PM

We've got the whole family in on this one!

If you tie knots in the rope, how much rope is used up?

[Itzik: for simplicity you can assume that knots don't consume any part of the rope.]

Jeremy2/12/2007 8:10:01 PM