Grades 3-4 Video Solutions 2020-2020Levels34prob19

Video Transcription

Problem number 19. The queen tries to find out the three names of Rumpelstiltskin's wife. She asks, are you called Adele Lily Cleo? Are you called Adele Laura Cora? Are  you called Abby Laura Cleo? Each time exactly one name and its position are right. What is the name of Rumpelstiltskin's wife? A. Abby Lily Cora, B. Abby Laura Cora,  C. Adele Laura Cleo, D. Adele Lily Cora, E. Abby Laura Cleo.  Look at the queen's questions and also at the answers. We see that we have two choices for the first name, either Adele or Abby. Two choices for the middle name, Lily or Laura.  And two choices for the third name, Cleo or Cora.  Also notice that in the questions, only one of the names is in the correct position.  If the first name were Adele, it would have to be the one name is correct in the first question  and in the second question, which meant that neither Lily nor Laura could be the middle name. Cleo and Cora could not be the third name. However, we know that those are the choices  that we have for the names. So we see that Abby is the only one that would work as the first name.  Following the same idea, the correct middle name will be the one that is different from the other two. So Lily is the correct middle name.  And finally, the third name is the one that only occurs once, which is Cora.  So the correct name is Abby Lily Cora, which is answer A.

Video Summary

The problem involves figuring out the names of Rumpelstiltskin's wife based on the queen's questions where each question indicates one correct name in the correct position. By analyzing the questions, we deduce that Abby is the correct first name as it is in the one position different from the others. Similarly, Lily is the correct middle name because it occurs in a unique position relative to the others. Finally, Cora is chosen as the third name, the only one occurring once in that position. Thus, the correct name is Abby Lily Cora, aligning with answer A.