SAT数学练习题—问答题 (9)

2016-02-25 11:50:14来源：网络

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　　参考答案

　　1.Correct Answer: 16

　　Explanation:

　　remember that dividing by a fraction is like multiplying by its inverse

　　1 x 3/1 + 2 x 6/2 + 3 x 7/3 = 3 + 6 + 7 = 16

　　2.Correct Answer: 6

　　Explanation:

　　If we imagine line segment PQ as the hypotenuse of a right triangle, we can see that the vertical distance between P and Q = 3 and the horizontal distance = 5 (Because the slope = difference in the y coordinates - difference in the x coordinates)

　　Since P is one unit to the right of the origin on the x-axis, Q must be 5 units to the right of that and so is at 6 units on the x-axis.

　　3.Correct Answer: 12.5

　　Explanation:

　　If you draw a diagram you will see there are two similar triangles involved.

　　The ratio of the trees will be equal to the ratio of their shadows

　　Let the height of the second tree = h; h/50 = 100/80; h = 50 x 100/80 = 62.5

　　The difference in their heights is 12.5

　　4.Correct Answer: 3.5

　　Explanation:

　　p² - q² = (p - q) (p + q)

　　12 = (p - q) (4)

　　p - q = 3; now add this to p + q = 4

　　2p = 7; p = 7/2

　　5.Correct Answer: 10

　　Explanation:

　　To get the average, add all three terms to get

　　2x + 2y + 2z = 60

　　So x + y + z = 30; and their average = 30/3 = 10

　　6.Correct Answer: 21.4

　　Explanation:

　　On the first day he harvests 2/7 of the area; on the second, twice as much (4/7); on the last day he harvests what�s left = 1 - 6/7 = 1/7

　　1/7 of 149.8 = 21.4

　　7.Correct Answer: 50

　　Explanation:

　　The odometer indicates (incorrectly) that 60 miles have been covered. The actual distance covered will be 5/6 x 60 = 50 miles.

　　8.Correct Answer: 5

　　Explanation:

　　The mode is the value that occurs most often. There are 10 pupils who obtain 80 marks, making 80 the most common score, and the mode.

　　The median is the middle term in the ranked series of scores. Since there are 25 pupils, the middle term will be 13th in the series. The top ten scores are all of 80, and the 13th score will occur in the next group of scores of 75. The median = 75.

　　The difference between mode and median = 80 - 75 = 5

　　9.Correct Answer: 71

　　Explanation:

　　If the average score does not change when Tina�s score is added, her score must be equal to the average score. The average = (80x10 + 5x75 + 5x70 + 2x60 + 2x55 + 1x20)/25

　　800 + 375 + 350 + 120 + 110 + 20 = 1055; 1775/25 = 71

　　10.Correct Answer: 1.4

　　Explanation:

　　We need to add the values of | d |. We need to remove all the minus signs because we need the absolute values of d. Hence, S = 0.1 + 0.2 + 0.3 + 0.1 + 0.4 + 0.3 = 1.4

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