AMC8试题汇编19992012.pdf

USA AMC 8 1999 1(6?3) + 4 (2 1) = 5. To make this statement true, the question mark between the 6 and the 3 should be replaced by (A) (B) (C) +(D) (E) None of these 2What is the degree measure of the smaller angle formed by the hands of a clock at 10 oclock? (A) 30(B) 45(C) 60(D) 75(E) 90 3Which triplet of numbers has a sum NOT equal to 1? (A) (1/2,1/3,1/6)(B) (2,2,1)(C) (0.1,0.3,0.6)(D) (1.1,2.1,1.0)(E) (3/2,5/2,5) 4The diagram shows the miles traveled by bikers Alberto and Bjorn. After four hours, about how many more miles has Alberto biked than Bjorn? Bjorn Alberto 012345 0 15 30 45 60 75 H O U R S M I L E S (A) 15(B) 20(C) 25(D) 30(E) 35 5A rectangular garden 50 feet long and 10 feet wide is enclosed by a fence. To make the garden larger, while using the same fence, its shape is changed to a square. By how many square feet does this enlarge the garden? (A) 100(B) 200(C) 300(D) 400(E) 500 6 Bo, Coe, Flo, Joe, and Moe have diff erent amounts of money. Neither Jo nor Bo has as much money as Flo. Both Bo and Coe have more than Moe. Jo has more than Moe, but less than Bo. Who has the least amount of money? (A) Bo(B) Coe(C) Flo(D) Joe(E) Moe 7The third exit on a highway is located at milepost 40 and the tenth exit is at milepost 160. There is a service center on the highway located three-fourths of the way from the third exit to the tenth exit. At what milepost would you expect to fi nd this service center? (A) 90(B) 100(C) 110(D) 120(E) 130 / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 1 USA AMC 8 1999 8Six squares are colored, front and back, (R = red, B = blue, O = orange, Y = yellow, G = green, and W = white). They are hinged together as shown, then folded to form a cube. The face opposite the white face is RB GY W O (A) B(B) G(C) O(D) R(E) Y 9 Three fl ower beds overlap as shown. Bed A has 500 plants, bed B has 450 plants, and bed C has 350 plants. Beds A and B share 50 plants, while beds A and C share 100. The total number of plants is A BC (A) 850(B) 1000(C) 1150(D) 1300(E) 1450 10 A complete cycle of a traffi c light takes 60 seconds. During each cycle the light is green for 25 seconds, yellow for 5 seconds, and red for 30 seconds. At a randomly chosen time, what is the probability that the light will NOT be green? (A) 1 4 (B) 1 3 (C) 5 12 (D) 1 2 (E) 7 12 11 Each of the fi ve numbers 1, 4, 7, 10, and 13 is placed in one of the fi ve squares so that the sum of the three numbers in the horizontal row equals the sum of the three numbers in the vertical column. The largest possible value for the horizontal or vertical sum is / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 2 USA AMC 8 1999 (A) 20(B) 21(C) 22(D) 24(E) 30 12The ratio of the number of games won to the number of games lost (no ties) by the Middle School Middies is 11 : 4 . To the nearest whole percent, what percent of its games did the team lose? (A) 24(B) 27(C) 36(D) 45(E) 73 13The average age of the 40 members of a computer science camp is 17 years. There are 20 girls, 15 boys, and 5 adults. If the average age of the girls is 15 and the average age of the boys is 16, what is the average age of the adults? (A) 26(B) 27(C) 28(D) 29(E) 30 14In trapezoid ABCD , the sides AB and CD are equal. The perimeter of ABCD is A BC D 8 16 3 (A) 27(B) 30(C) 32(D) 34(E) 48 15 Bicycle license plates in Flatville each contain three letters. The fi rst is chosen from the set C,H,L,P,R, the second from A,I,O, and the third from D,M,N,T. When Flatville needed more license plates, they added two new letters. The new letters may both be added to one set or one letter may be added to one set and one to another set. What / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 3 USA AMC 8 1999 is the largest possible number of ADDITIONAL license plates that can be made by adding two letters? (A) 24(B) 30(C) 36(D) 40(E) 60 16Toris mathematics test had 75 problems: 10 arithmetic, 30 algebra, and 35 geometry prob- lems. Although she answered 70% of the arithmetic, 40% of the algebra, and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% of the problems right. How many more problems would she have needed to answer correctly to earn a 60% passing grade? (A) 1(B) 5(C) 7(D) 9(E) 11 17Problems 17, 18, and 19 refer to the following: At Central Middle School the 108 students who take the AMC8 meet in the evening to talk about problems and eat an average of two cookies apiece.Walter and Gretel are baking Bonnies Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: 1.5 cups fl our, 2 eggs, 3 tablespoons butter, 3/4 cups sugar, and 1 package of chocolate drops. They will make only full recipes, not partial recipes. Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.) (A) 1(B) 2(C) 5(D) 7(E) 15 18Problems 17, 18, and 19 refer to the following: At Central Middle School the 108 students who take the AMC8 meet in the evening to talk about problems and eat an average of two cookies apiece.Walter and Gretel are baking Bonnies Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: 1.5 cups fl our, 2 eggs, 3 tablespoons butter, 3/4 cups sugar, and 1 package of chocolate drops. They will make only full recipes, not partial recipes. They learn that a big concert is scheduled for the same night and attendance will be down 25%. How many recipes of cookies should they make for their smaller party? (A) 6(B) 8(C) 9(D) 10(E) 11 19Problems 17, 18, and 19 refer to the following: At Central Middle School the 108 students who take the AMC8 meet in the evening to talk about problems and eat an average of two cookies apiece.Walter and Gretel are baking Bonnies Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: 1.5 cups fl our, 2 eggs, 3 tablespoons butter, 3/4 cups sugar, and 1 package of chocolate drops. They will make only full recipes, not partial recipes. / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 4 USA AMC 8 1999 The drummer gets sick. The concert is cancelled. Walter and Gretel must make enough pans of cookies to supply 216 cookies. There are 8 tablespoons in a stick of butter. How many sticks of butter will be needed? (Some butter may be left over, of course.) (A) 5(B) 6(C) 7(D) 8(E) 9 20Figure 1 is called a ”stack map.” The numbers tell how many cubes are stacked in each position. Fig. 2 shows these cubes, and Fig. 3 shows the view of the stacked cubes as seen from the front. Which of the following is the front view for the stack map in Fig. 4? Figure 1Figure 2Figure 3Figure 4 12 34 131 224 (A)(B)(C)(D)(E) 21The degree measure of angle A is / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 5 USA AMC 8 1999 40 100 110 A (A) 20(B) 30(C) 35(D) 40(E) 45 22 In a far-off land three fi sh can be traded for two loaves of bread and a loaf of bread can be traded for four bags of rice. How many bags of rice is one fi sh worth? (A) 3 8 (B) 1 2 (C) 3 4 (D) 22 3 (E) 31 3 23Square ABCD has sides of length 3. Segments CM and CN divide the squares area into three equal parts. How long is segment CM ? A M BC DN (A) 10 (B) 12 (C) 13 (D) 14 (E) 15 / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 6 USA AMC 8 1999 24When 19992000is divided by 5 , the remainder is (A) 4(B) 3(C) 2(D) 1(E) 0 25Points B,D , and J are midpoints of the sides of right triangle ACG . Points K, E, I are midpoints of the sides of triangle , etc. If the dividing and shading process is done 100 times (the fi rst three are shown) and AC = CG = 6, then the total area of the shaded triangles is nearest ABC D E F G H I J K L (A) 6(B) 7(C) 8(D) 9(E) 10 The problems on this page are copyrighted by the Mathematical Association of Americas American Mathematics Competitions. / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 7 USA AMC 8 2000 1Aunt Anna is 42 years old. Caitlin is 5 years younger than Brianna, and Brianna is half as old as Aunt Anna. How old is Caitlin? (A) 15(B) 16(C) 17(D) 21(E) 37 2Which of these numbers is less than its reciprocal? (A) 2(B) 1(C) 0(D) 1(E) 2 3How many whole numbers lie in the interval between 5 3 and 2? (A) 2(B) 3(C) 4(D) 5 (E) infi nitely many 4In 1960 only 5% of the working adults in Carlin City worked at home. By 1970 the ”at-home” work force increased to 8%. In 1980 there were approximately 15% working at home, and in 1990 there were 30%. The graph that best illustrates this is 1960 1970 1980 1990 10 20 30 % 1960 1970 1980 1990 10 20 30 % 1960 1970 1980 1990 10 20 30 % 1960 1970 1980 1990 10 20 30 % 1960 1970 1980 1990 10 20 30 % (A)(B)(C) (D)(E) 5Each principal of Lincoln High School serves exactly one 3-year term. What is the maximum number of principals this school could have during an 8-year period? (A) 2(B) 3(C) 4(D) 5(E) 8 6Figure ABCD is a square. Inside this square three smaller squares are drawn with the side lengths as labeled. The area of the shaded L-shaped region is / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 1 USA AMC 8 2000 A BC D 1 1 3 3 1 1 (A) 7(B) 10(C) 12.5(D) 14(E) 15 7 What is the minimum possible product of three diff erent numbers of the set 8,6,4,0,3,5,7? (A) 336(B) 280(C) 210(D) 192(E) 0 8Three dice with faces numbered 1 through 6 are stacked as shown. Seven of the eighteen faces are visible, leaving eleven faces hidden (back, bottom, between). The total number of dots NOT visible in this view is (A) 21(B) 22(C) 31(D) 41(E) 53 / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 2 USA AMC 8 2000 9Three-digit powers of 2 and 5 are used in this ”cross-number” puzzle.What is the only possible digit for the outlined square? ACROSSDOWN 2. 2m1. 5n 1 2 (A) 0(B) 2(C) 4(D) 6(E) 8 10Ara and Shea were once the same height. Since then Shea has grown 20% while Ara has grow half as many inches as Shea. Shea is now 60 inches tall. How tall, in inches, is Ara now? (A) 48(B) 51(C) 52(D) 54(E) 55 11The number 64 has the property that it is divisible by its units digit.How many whole numbers between 10 and 50 have this property? (A) 15(B) 16(C) 17(D) 18(E) 20 12A block wall 100 feet long and 7 feet high will be constructed using blocks that are 1 foot high and either 2 feet long or 1 foot long (no blocks may be cut). The vertical joins in the blocks must be staggered as shown, and the wall must be even on the ends. What is the smallest number of blocks needed to build this wall? / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 3 USA AMC 8 2000 (A) 344(B) 347(C) 350(D) 353(E) 356 13In triangle CAT, we have ACT = ATC and CAT = 36. If TR bisects ATC, then CRT = A TC R (A) 36(B) 54(C) 72(D) 90(E) 108 14What is the units digit of 1919+ 9999? (A) 0(B) 1(C) 2(D) 8(E) 9 15Triangles ABC, ADE, and EFG are all equilateral. Points D and G are midpoints of AC and AE, respectively. If AB = 4, what is the perimeter of fi gure ABCDEFG? AB C DE FG (A) 12(B) 13(C) 15(D) 18(E) 21 / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 4 USA AMC 8 2000 16In order for Mateen to walk a kilometer (1000m) in his rectangular backyard, he must walk the length 25 times or walk its perimeter 10 times. What is the area of Mateens backyard in square meters? (A) 40(B) 200(C) 400(D) 500(E) 1000 17 The operation is defi ned for all nonzero numbers by ab = a2 b . Determine (12)3 1 (2 3). (A) 2 3 (B) 1 4 (C) 0(D) 1 4 (E) 2 3 18Consider these two geoboard quadrilaterals. Which of the following statements is true? I II (A) The area of quadrilateral I is more than the area of quadrilateral II. (B) The area of quadrilateral I is less than the area of quadrilateral II. (C) The quadrilaterals have the same area and the same perimeter. (D) The quadrilaterals have the same area, but the perimeter of I is more than the perimeter of II. (E) The quadrilaterals have the same area, but the perimeter of I is less than the perimeter of II. 19Three circular arcs of radius 5 units bound the region shown. Arcs AB and AD are quarter- circles, and arc BCD is a semicircle. What is the area, in square units, of the region? / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 5 USA AMC 8 2000 A B C D (A) 25(B) 10 + 5(C) 50(D) 50 + 5(E) 25 20You have nine coins: a collection of pennies, nickels, dimes, and quarters having a total value of $1.02, with at least one coin of each type. How many dimes must you have? (A) 1(B) 2(C) 3(D) 4(E) 5 21Keiko tosses one penny and Ephraim tosses two pennies. The probability that Ephraim gets the same number of heads that Keiko gets is (A) 1 4 (B) 3 8 (C) 1 2 (D) 2 3 (E) 3 4 22A cube has edge length 2. Suppose that we glue a cube of edge length 1 on top of the big cube so that one of its faces rests entirely on the top face of the larger cube. The percent increase in the surface area (sides, top, and bottom) from the original cube to the new solid formed is closest to / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 6 USA AMC 8 2000 (A) 10(B) 15(C) 17(D) 21(E) 25 23 There is a list of seven numbers. The average of the fi rst four numbers is 5, and the average of the last four numbers is 8. If the average of all seven numbers is 64 7, then the number common to both sets of four numbers is (A) 53 7 (B) 6(C) 64 7 (D) 7(E) 73 7 24If A = 20and AFG = AGF, then B + D = A B C D E F G (A) 48(B) 60(C) 72(D) 80(E) 90 25The area of rectangle ABCD is 72. If point A and the midpoints of BC and CD are joined to form a triangle, the area of that triangle is AB CD / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 7 USA AMC 8 2000 (A) 21(B) 27(C) 30(D) 36(E) 40 The problems on this page are copyrighted by the Mathematical Association of Americas American Mathematics Competitions. / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 8 USA AMC 8 2001 1Caseys shop class is making a golf trophy. He has to paint 300 dimples on a golf ball. If it takes him 2 seconds to paint one dimple, how many minutes will he need to do his job? (A) 4(B) 6(C) 8(D) 10(E) 12 2Im thinking of two whole numbers. Their product is 24 and their sum is 11. What is the larger number? (A) 3(B) 4(C) 6(D) 8(E) 12 3Granny Smith has $63. Elberta has $2 more than Anjou and Anjou has one-third as much as Granny Smith. How many dollars does Elberta have? (A) 17(B) 18(C) 19(D) 21(E) 23 4 The digits 1, 2, 3, 4 and 9 are each used once to form the smallest possible even fi ve-digit number. The digit in the tens place is (A) 1(B) 2(C) 3(D) 4(E) 9 5 On a dark and stormy night Snoopy suddenly saw a fl ash of lightning. Ten seconds later he heard the sound of thunder. The speed of sound is 1088 feet per second and one mile is 5280 feet. Estimate, to the nearest half-mile, how far Snoopy was from the fl ash of lightning. (A) 1(B) 11 2 (C) 2(D) 21 2 (E) 3 6 Six trees are equally spaced along one side of a straight road. The distance from the fi rst tree to the fourth is 60 feet. What is the distance in feet between the fi rst and last trees? (A) 90(B) 100(C) 105(D) 120(E) 140 7Problems 7, 8 and 9 are about these kites. To promote her schools annual Kite Olympics, Genevieve makes a small kite and a large kite for a bulletin board display. The kites look like the one in the diagram. For her small kite Genevieve draws the kite on a one-inch grid. For the large kite she triples both the height and width of the entire grid. / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 1 USA AMC 8 2001 What is the number of square inches in the area of the small kite? (A) 21(B) 22(C) 23(D) 24(E) 25 8Problems 7, 8 and 9 are about these kites. Genevieve puts bracing on her large kite in the form of a cross connecting opposite corners of the kite. How many inches of bracing material does she need? (A) 30(B) 32(C) 35(D) 38(E) 39 9Problems 7, 8 and 9 are about these kites. / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 2 USA AMC 8 2001 The large kite is covered with gold foil. The foil is cut from a rectangular piece that just covers the entire grid. How many square inches of waste material are cut off from the four corners? (A) 63(B) 72(C) 180(D) 189(E) 264 10 A collector off ers to buy state quarters for 2000% of their face value. At that rate how much will Bryden get for his four state quarters? (A) 20 dollars(B) 50 dollars(C) 200 dollars(D) 500 dollars(E) 2000 dollars 11Points A,B,C and D have these coordinates: A(3,2),B(3,2),C(3,2) and D(3,0). The area of quadrilateral ABCD is (A) 12(B) 15(C) 18(D) 21(E) 24 / This fi le was downloaded from the AoPS Math Olympiad Resources PagePage 3 USA AMC 8 2001 12If a b = a+b ab , then (6 4) 3 = = (A) 4(B) 13(C) 15(D) 30(E) 72 13Of the 36 students in Richelles class, 12 prefer chocolate pie, 8 prefer apple, and 6 prefer blueberry.Half of the remaining students prefer cherry pie and half prefer lemon.For Richelles pie graph showing this data, how many degrees should she use for cherry pie? (A) 10(B) 20(C) 30(D) 50(E) 72 14 Tyler has entered a buff et l