Logic Grid Puzzle (Above the Summits, new tips)

Question

UPDATE 20-01-13: I sent an email to the admin of the site, pointing out the problem. The tip 1 has now been corrected and the puzzle can be solved. The "Laundry Time" puzzle I mentioned in this post has been fixed as well.

I'm trying to solve the new version of the "Above the Summits" grid puzzle. I wonder if I'm doing something wrong. It seems to me that the tips contradict each other.

The tips are:

1. The explorer who needed 10 days to climb a mountain was either the explorer who climbed the Aconcagua or the explorer who climbed in 1970.
2. The 1970 climbing took longer than the 1990 climbing.
3. Of the explorer Ludwig and the explorer Otto, one climbed in 1990 and the other climbed the Kilimanjaro.
4. The Aconcagua needed 5 more days to be climbed than the mountain climbed in 1970.
5. The mountain climbed in 1980 needed 5 more days to be climbed than the mountain climbed by Otto.
6. The Everest was either climbed by Edmund or climbed in 1980.
7. The mountain climbed in 1990 need 5 fewer days than the mountain climbed by Edmund.

Along with many other attempts, the most logical way I was trying to find the solution was this:

• Tip 1: Since the amount of days required for climbing are 5, 10, 15 and 20, the "10 days climb" mountain can't be Aconcagua. That's because days of 1970 > days of 1990 (tip 2) and days to Aconcagua = days of 1970 plus 5 (tip 4), which means at least 15 days to reach Aconcagua was needed. Thus, the 10 days climbing would have happened in 1970.
• Aconcagua = 15 days (tip 4)
• 1990 climbing = 5 days. (1970 = 10 days, and tip 2).
• 1970 = 10 days = Edmund (Tip 7.)
• As for the tip 3 and 1990/Kilimanjaro, which one is Ludwig and which one Otto? Here's how I thought it to be: 1980 mountain is Otto's mountain plus 5 days (tip 5). On the other hand, Edmund's mountain is 1990 mountain plus 5 days (tip 7). Now because tip 6 implies that Edmund didn't climb in 1980 (as only one of those applies to Everest), Otto's year can't be 1990 either. So, Otto would have climbed to Kilimanjaro and Ludwig would have climbed in 1990. --> Ludwig = 5 days = 1990. And Otto = Kilimanjaro.
• Since Ludwig (1990) has 5 days and Edmund (1970) 10 days, and Otto can't have 20 days (tip 5, "5 more days than Otto"), Otto would have 15 days. But now, 15 days is already related to Aconcagua and Otto would be climbing to Kilimanjaro. What to do now?

I think there is an error or errors in the tips, and I have made many attempts to find it trying different solutions (making assumptions where a possible typo could be), but it's all too complicated. Have any of you managed to point out the possible error either in the tips or in my attempt above?

I did find an error in the tips of "Laundry Time", since I managed to find the right solution, but that was much easier, because you can see two of the colors can't be told apart since neither of them is mentioned. This mountain climbing problem is so much more difficult. I would like to enjoy these grid puzzles, and it's a shame you can't even actually solve them even if you try many times. Maybe I just should stick with the "Logic equations"", they are always solvable.

Answer 1

I wrote a little program to brute-force this. I can confirm that there appear to be no solutions. If we delete tip 1 there are two; if we delete tip 2 or tip 6 there are still none; if we delete tip 3 or tip 4 there are eight; if we delete tip 5 there are four; if we delete tip 7 there is exactly one solution.

So the trouble is unlikely to lie in tip 2 or 6; it could in principle be in any of the others. There are probably many ways to fix it up; one is to replace "5" with "15" in tip 7. (That gives the same single solution as we get by deleting tip 7 altogether.)

I think the main discovery here is that Brainzilla isn't a reliable source of high-quality puzzles. But I don't think that's a huge surprise.