Algebra:Algebra:Fun with Calendars!Fun with Calendars!

Middle SchoolMiddle SchoolOrOr

High School Warm-Up ActivityHigh School Warm-Up Activity

SeptemberSeptemberSundaySunday MondayMonday TuesdayTuesday WednesdayWednesday ThursdayThursday FridayFriday SaturdaySaturday

11

22 33 44 55 66 77 88

99 1010 1111 1212 1313 1414 1515

1616 1717 1818 1919 2020 2121 2222

2323 2424 2525 2626 2727 2828 2929

3030

ObjectObject

When given only the sum, how When given only the sum, how do we determine what the dates do we determine what the dates are?are?

3636

SolutionSolution Let’s assume that the first day is nLet’s assume that the first day is n So, the second day is n + 1, the third day So, the second day is n + 1, the third day

is n + 7, the fourth day is n + 8.is n + 7, the fourth day is n + 8. Then we have:Then we have:

n + (n + 1) + (n + 7) + (n + 8)n + (n + 1) + (n + 7) + (n + 8) 4n + 164n + 16

4n + 16 = 364n + 16 = 36 4n = 204n = 20 n = 5n = 5

Mental Math Tip:Mental Math Tip: Factor before solving:Factor before solving:

4(n + 4) = 364(n + 4) = 36 n + 4 = 9n + 4 = 9 n = 5n = 5

So the dates are September 5, 6, 12, 13So the dates are September 5, 6, 12, 13

Try again with 88…Try again with 88…

ReferencesReferences Tara Taylor’s WebsiteTara Taylor’s Website

www.stfx.ca/people/ttaylorwww.stfx.ca/people/ttaylor

Cynthia Lanius’ LessonsCynthia Lanius’ Lessons http://math.rice.edu/~lanius/Lessons/calen.hthttp://math.rice.edu/~lanius/Lessons/calen.ht

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