「Answer」AMC8 -- 2012年真题解析与视频讲解
北京联盟_本文原题：AMC8 -- 2012年真题解析与视频讲解
Problem 1
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Answer: E
Solution:
Since Rachelle uses 3 pounds of meat to make 8 hamburgers, she uses 3/8 pounds of meat to make one hamburger. She'll need 24 times that amount of meat for 24 hamburgers, 3/8*24=9.Problem 2
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Answer: B
Solution:
There are 24hours /8hours =3 births and one death everyday in East Westmore. Therefore, the population increases by 3-1=2 people everyday. Thus, there are 2*365=730 people added to the population every year. Rounding, we find the answer is 700.Problem 3
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Answer: B
Solution:
The problem wants us to find the time of sunset and gives us the length of daylight and time of sunrise. Adding, we find that the time of sunset is 6:57am+10:24=17:21. =5：21 pm.Problem 4
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Answer: C
Solution:
Peter ate 1+1/2=3/2 slices. The pizza has 12 slices total. Taking the ratio of the amount of slices Peter ate to the amount of slices in the pizza, we find that Peter ate (3/2)/12=3/24=1/8 of the pizza.Problem 5
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Answer: E
Solution:
The figure is the same height on both sides, so the sum of the lengths contributing to the height on the left side will equal the sum of the lengths contributing to the height on the left side. 1+1+1+2+x=1+2+1+6 ; =>x=5.Problem 6
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Answer: E
Solution:
The area of the photograph is 8*10=80 square inches. The height of the whole frame (including the photograph) would be 8+2+2=12, the width of the whole frame would be 10+2+2=14. Therefore, the area of the whole figure would be 12*14=168 square inches. Subtracting the area of the photograph from the area of both the frame and photograph, we find the answer to be 168-80=88.Problem 7
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Answer: B
Solution:
Isabella wants an average grade of 95 on her 4 tests; this also means that she wants the sum of her test scores to be at least 95*4=380. She's already taken two tests, which sum to 97+91=188, which means she needs 192 more points to achieve her desired average. In order to minimize the score on the third test, we assume that Isabella will receive all 100 points on the fourth test. Therefore, the lowest Isabella could have scored on the third test would be192-100=92.Problem 8
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Answer: D
Solution:
First ,use the 20% discount of coupon, then use the half price of the advertise. Your should pay (1-20%)*0.5=0.4 for any item. Thus the discount is 1-0.4=0.6=60%.Problem 9
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Answer: C
Solution:
Let the number of two-legged birds be x and the number of four-legged mammals be y. We can now use systems of equations to solve this problem.Write two equations:2x+4y=522;x+y=200;solving the equations, we get x=139.Problem 10
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Answer: D
Solution:
For this problem, all we need to do is find the amount of valid 4-digit numbers that can be made from the digits of 2012. There can be only two leading digits, namely 1 or 2.When the leading digit is 1, you can make 3 such numbers.When the leading digit is 2, you can make 6 such numbers.Summing the amounts of numbers, we find that there are 9 such numbers.Problem 11
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