Answer :
Answer:
On Friday, Stan said "Yesterday, I lied" which is true based on the fact that he lied about saying the truth yesterday while, Fren said "Yesterday, I lied" which is true because he's saying the truth about what happened on Thursday
Step-by-step explanation:
Given:
- Stan's Pattern
Lies on: Friday, Saturday, Sunday
Tells the truth on Monday, Tuesday, Wednesday, and Thursday - Fred's Pattern
Lies on: Tuesday, Wednesday, Thursday
Tells the truth on Friday, Saturday, Sunday, and Monday
Let's validate each scenario
Monday
Stan (truth) ➜ Yesterday was Sunday (he lied)
Fred (truth) ➜ Yesterday was Sunday (he told the truth)
Fred contradicts himself
Tuesday
Stan (truth) ➜ Yesterday was Monday (he told the truth)
Fred (lie) ➜ Yesterday was Monday (he told the truth)
Fred contradicts himself
Wednesday
Stan (truth) ➜ Yesterday was Tuesday (he told the truth)
Fred (lie) ➜ Yesterday was Tuesday (he lied)
Stan contradicts himself
Thursday
Stan (truth) ➜ Yesterday was Wednesday (he told the truth)
Fred (lie) ➜ Yesterday was Wednesday (he lied)
Stan contradicts himself
Friday
Stan (lie) ➜ Yesterday was Thursday (he told the truth)
Fred (truth) ➜ Yesterday was Thursday (he lied)
Valid - both statements are consistent
Saturday
Stan (lie) ➜ Yesterday was Friday (he lied)
Fred (truth) ➜ Yesterday was Friday (he told the truth)
Fred contradicts himself
Sunday
Stan (lie) ➜ Yesterday was Saturday (he lied)
Fred (truth) ➜ Yesterday was Saturday (he told the truth)
Fred contradicts himself
The only valid day where both Stan and Fred can say, "Yesterday I lied," and their statements are consistent is Friday.
