Grades 9-10 Video Solutions 2021-video 2021 9-10/1

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Problem number one states, each year the third Thursday in March is named Kangaroo Day. The dates of Kangaroo Day for the next few years are shown below, with one error.  Which date is wrong? So rather than trying to calculate the exact day Kangaroo Day lands on each year, let's  first take a look at the range of days that the third Saturday of March could even fall on. So let's start off here with an abstract calendar with 31 days on it, because the month  of March has 31 days. In this case we will assume that the first falls on a Sunday, but soon we will be relaxing this assumption. Let's highlight each of the weeks.  Red will be the first week, yellow the second, and green the third. Let's also pull up the answers and see what days Kangaroo Day can fall on.  So if we assume the first falls on a Sunday, then the Kangaroo Day, the third Thursday of the month, will be on the 19th. This means that March 19th, 2026 is a possible outcome.  Note this does not mean that in 2026 Kangaroo Day falls on the 19th, it simply means that it is not impossible for it to.  Now let's relax our assumption and say the first falls on Monday. This would mean Kangaroo Day would fall on the 18th. That's not an answer, so let's keep going.  Tuesday would fall on the 17th, Wednesday would fall on the 16th, Thursday would fall on the 15th, Friday would fall on the third Thursday Kangaroo Day, not the second, so  would be the 21st, and Saturday would fall on the 20th.  It never fell on the 14th, which means that it is impossible for the 14th of the month to be the third Thursday of March, and this makes sense as the 14th is in the second week  of the month. So the question asked us, which date is wrong? The answer is March 14th, 2024. Letter C.

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