Grades 7-8 Video Solutions 2022-2022_7-8

Video Transcription

Question 27. Mowgli asks a zebra and a panther what day it is. The zebra always lies on Monday, Tuesday, and Wednesday, and always tells the truth on the other days.  The panther always lies on Thursday, Friday, and Saturday, and always tells the truth on the other days. The zebra says, Yesterday was one of my lying days.  The panther says, Yesterday was also one of my lying days. What day is it? We can draw out a table that shows the days of the week and then the zebra and the panther.  We know that the zebra always lies on Monday, Tuesday, and Wednesday, and the panther always lies on Thursday, Friday, and Saturday,  so we can mark these as red because they are their lying days. Now, if we, for example, look at Friday. The zebra said, Yesterday was one of my lying days.  On Friday, the zebra tells the truth. If this was the truth, then Thursday would be marked as red. It is not, so this cannot be the answer.  If we look at Thursday, the zebra says, Yesterday was one of my lying days, and we can confirm. The day prior, the zebra would have lied.  Now, the panther says, Yesterday was also one of my lying days, which is not true. But since Thursday is the panther's lying day, we would expect the panther to lie.  So the day is Thursday. The correct answer is A.

Video Summary

Mowgli asks a zebra and a panther which day it is. The zebra lies on Monday to Wednesday and the panther lies on Thursday to Saturday. The zebra claims that yesterday was one of its lying days, while the panther says the same about itself. Analyzing the statements, if it were Thursday, the zebra would be telling the truth about Wednesday being a lying day. Meanwhile, the panther, which lies on Thursdays, would falsely claim that Wednesday was its lying day too. Therefore, the conclusion is that it must be Thursday. The answer is Thursday.

Keywords

Mowgli

zebra

panther

lying days

Thursday