Lion and Unicorn #1 (Solution)

Let’s review the situation give!

these pic were taken from http://www.istockphoto.com.

In a forest of forgetfulness, there were lion and unicorn. The lion lies every Monday, Tuesday and Wednesday and the other days he speaks the truth. The unicorn lies on Thursdays, Fridays and Saturdays, however the other days of the week he speaks the truth.

Lion said, “Yesterday I was lying.”

Unicorn replied, “So was I.”

Which day did they say that?

To know what day they said that, we have to draw their lying schedule first.

Now, time to go checking what Lion said!

Lion said, “Yesterday I was lying.”

If he’s speaking truth –yesterday he had been lying, and the day he’s speaking he was speaking the truth– it must be Thursday.

But if he’s lying –yesterday he had been speaking truth, and the day he’s speaking he was lying– it must be Monday.

So, it might be Thursday or Monday.

It’s Unicorn’s turn!

Unicorn replied, “So was I” –yesterday he was lying.

If he’s speaking truth –yesterday he had been lying, and the day he’s speaking he was speaking the truth– it must be Sunday.

But if he’s lying –yesterday he had been speaking truth, and the day he’s speaking he was lying– it must be Thursday.

So, it might be Sunday or Thursday.

Knowing that they’re talking on the same day, it must be Thursday (the day for lion to tell truth and for unicorn to lie) because they both had “Thursday-possibility”.

P.S.: This brain teaser I copied from Brain Teasers (http://brainden.com/logic-problems.htm). Just on click on that link, then you’ll get more brain teasers to tease your brain or even just to ease your boring day. When you get stuck, you can visit brain teasers forum to get extra “clues” from them whom have tried to solve it (but for me, it’s better to do it by myself as I did in solving this quiz).