「Answer」AMC8 -- 2000年真题解析
北京联盟_本文原题： AMC8 -- 2000年真题解析
Problem 1
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Answer: B
Solution:
Since Brianna is half of Aunt Anna's age this means that Brianna is 21 years old. Now we just find Caitlin's age by doing 21-5=16.Problem 2
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Answer: A
Solution:
The number 0 has no reciprocal, the reciprocal of 1 is 1, the reciprocal of -1 is -1. This leaves only 2 ,-2. The reciprocal of 2 is 1/2, but 2 is not less than 1/2. The reciprocal of -2 is -1/2, -2 is less than-1/2, so it is A.Problem 3
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Answer: D
Solution:
The smallest whole number in the interval is 2 because 5/3 is more than 1 but less than 2. The largest whole number in the interval is 6 because 2Pi is more than 6 but less than 7. There are five whole numbers in the interval. They are 2,3,4,5,6, so the answer is D.Problem 4
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Answer: E
Solution:
The data are 1990(5%), 1970(8%), 1980(15%) ， and 1990(30%). Only one of these graphs has the answer and that is choice E.Problem 5
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Answer: C
Solution:
If the first year of the 8-year period was the final year of a principal's term, then in the next six years two more principals would serve, and the last year of the period would be the first year of the fourth principal's term. Therefore, the maximum number of principals who can serve during an 8-year period is 4.Problem 6
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Answer: A
Solution:
Solution: A (area)
The shaded area can be divided into three regions: one small square with side 1, and two rectangles with a length and width of 1 and 3. The sum of these three areas is 1*1+3*1+1*3=7.Problem 7
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Answer: B
Solution:
The only way to get a negative product using three numbers is to multiply one negative number and two positives or three negatives. Only two reasonable choices exist: (-8)*(-6)*(-4)=-192 ; (-8)*5*7=-280. The latter is smaller, so the answer is 280.Problem 8
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Answer: D
Solution:
The numbers on one die total 1+2+3+4+5+6=21, so the numbers on the three dice total 63. Numbers 1,1,2,3,4,5,6 are visible, and these total 22. This leaves 63-22=41 not seen.Problem 9
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Answer: D
Solution:
The 3-digit powers of 5 are 125 and 625, so space 2 is filled with a 2. The only 3-digit power of 2 beginning with 2 is 256, so the outlined block is filled with a 6.Problem 10
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Answer: E
Solution:
Shea has grown 20%, if x was her original height, then 1.2x=60, so she was originally 60/1.2=50 inches tall which is a 60-50=10 inch increase. Ara also started off at 50 inches. Since Ara grew half as much as Shea, Ara grew 10/2=5 inches. Therefore, Ara is now 50+5=55 inches tall.Problem 11
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Answer: C
Solution:
U=0 gives no solutions, since no real numbers are divisible by 0;U=1 has 4 solutions, since all numbers are divisible by 1;U=2 has 4 solutions, since every number ending in 2 is even;U=3 has 1 solution:33;U=4 has 2 solutions: 24 and 44;U=5 has 4 solutions: every number ending in 5 is divisible by 5;U=6 has 1 solution: 36;U=7 has no solutions;U=8 has 1 solution: 48U=9 has no solutions.Totally we have 0+4+4+1+2+4+1+0+1+0=17 solutions.Problem 12
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