I don't understand a clue on a logic puzzle

[Cybr]

Hello, I'm beginner with logic puzzle solving.
Today I tried to solve this puzzle, but as I was blocked I asked for an hint.
The software answers me with the message you'll see on the picture, but I still don't understand the logic behind that.
Is someone can help me, please ?

Thanks in advance !

[admin]

Hi Cybr -

These hints can be a little confusing, but the logic behind them is fairly simple once you learn to recognize it.

The hint is telling you that Darlene and solar energy both have greater/lesser than clues relating them to different items in the same category at the same "step distance". So let's find those clues:

2. The sulfur oxide expert is scheduled 1 day before Darlene.

4. Elena is scheduled 1 day before the solar energy expert.

Based on your existing grid deductions, you also know that Elena == acid rain. Therefore, #4 can also be read as:

4. Acid rain is scheduled 1 day before the solar energy expert.

We know just by the rules of logic puzzles that since acid rain and sulfur oxide are two items in the same category, by default they must each be assigned to two different dates. And since clue #2 says Darlene = Sulfur Oxide + 1 day, and clue #4 says Solar Energy = Acid Rain + 1 day, and we know Acid Rain CANNOT be the same day as Sulfur Oxide, then we know that Darlene CANNOT be the same day as Solar Energy. Therefore you can mark an X between Darlene and Solar Energy.

This is definitely an advanced solving method, so don't feel too bad if you don't recognize it at first. What really helps with these types of deductions is simple note taking for all greater/lesser than clues. Use "==>" and "<==" to show one greater/less than, and "..." to show vague greater/lesser than when you don't know an exact amount. In other words, clues #2 and #4 can be notated as:

Sulfur Oxide ==> Darlene

Elena/Acid Rain ==> Solar Energy

When you see two items line up in your notes at the same "step distance" from two other items, you can often make these types of advanced logical deductions.

Hope that helps!

[Cybr]

Thank you very much for your answer : It helps a lot !