Mary’s top book shelf holds five books with thefollowing widths, in centimeters:6,12, 1,2.5, and5. What is the average book width, in centimeters?(A)1(B)2(C)3(D)4(E)52010 AMC 10 A, Problem #1—“The average of five values=the sum of the values÷5.”

Three identical squares and one rectangle are placedtogether to form one large square as shown.Thelength of the rectangle is how many times as largeas its width?2010 AMC 10 A, Problem #2—“The length of the rectangle is equal to three times theside length of the smaller square.”Diﬃculty:EasyNCTMStandard:GeometryStandardforGrades9–12:explorerelationships(includingcongruence and similarity) among classes of two- and three-dimensional geometric objects, makeand test conjectures about them, and solve problems involving them.

A ferry boat shuttles tourists to an island every hourstarting at 9amuntil its last trip starting at 3pm.One day the boat captain notes that on the 9amtripthere were 100 tourists on the ferry boat, and thaton each successive trip, the number of tourists was 1fewer than on the previous trip. How many touristsdid the ferry take to the island that day?(A)585(B)594(C)672(D)679(E)6942010 AMC 10 A, Problem #3—2010 AMC 12 A, Problem #2—“The ferry boat makes 7 trips to the island everyday.”

The area of a circle whose circumference is12πiskπ.What is the value ofk?2010 AMC 10 A, Problem #4—2010 AMC 12 A, Problem #1—“The circumference of a circle with radiusris2πr.”Diﬃculty:EasyNCTM Standard:Algebra Standard for Grades 9–12:use symbolic algebra to represent andexplain mathematical relationships.

Halfwaythrougha100-shotarcherytournament,Chelsea leads by 50 points. For each shot a bullseyescores 10 points, with other possible scores being 8,4, 2, and 0 points. Chelsea always scores at least 4points on each shot. Her nextnshots are bulleyes,which guarantees her victory. What is the minimumpossible value forn?(A)40(B)42(C)44(D)46(E)48