Grades 11-12 Video Solutions 2021-video 2021 11-12/24

Video Transcription

Problem number 24 states, five kangaroos named A, B, C, D, and E have one child each named lowercase a, b, c, d, and e.  In the first group photo shown, exactly two of the children are standing next to their mothers.  In the second group photo, exactly three of the children are standing next to their mothers. Whose child is lowercase a?  So first let's represent all of this information in an easier to understand format. So in this list where the arrow means is the parent of, two of these statements are correct.  In the next picture we have another five statements, and three of these are correct. So let's see if we can notice something about these two sets.  We might be able to notice that mothers A and C swap kids B and D, and further that mothers B, D, and E cycle kids A, C, and E.  In order for two statements to be right in the first one, and two wrong in the second one, the statements saying that A's child is D and C's child is B must be correct statements  in the first picture. So the remaining three statements are true in the second picture. And so we can conclude that D's child is child A.  So the question asked us, whose child is child A? The answer is D, letter D.

Video Summary

In this problem, five kangaroos (A, B, C, D, and E) each have a child (a, b, c, d, and e). Two photos are taken: in the first, two children are next to their mothers, and in the second, three are. After analyzing both sets of conditions, it is determined that initially, mothers A and C switched kids B and D, while mothers B, D, and E cycled kids A, C, and E. This analysis reveals that in the first scenario, A's child is D and C's child is B; thus, in the second scenario, D's child is determined to be child a.