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22: If one of the houses from the previous question is randomly selected, what is the probability that the selected house is a ranch?

　　(a) 110

　　(b) 47

　　(c) 37

　　(d) 0

　　(e) 2370

Answer:

The number of ranches is 30 and the total number of houses is 70, so the probability is 3070 = 37.

23: The AB side of the ABCD trapezoid is 4 and the BC side is 3. What is the area of the triangle ABD?

　　(a) 4

　　(b) 72

　　(c) 92

　　(d) 6

　　(e) 7

Answer:

The area of the ABD triangle is 12·AB·h, where h is the height from D onto AB, ED.

Since DEB angle is 90o and equal to angle BCD, EBCD is a rectangle and ED = BC = 3

The area is (12)·4·3 = 6.

24: The side AB of the ABCD square is 10, AE = ED and BF = FC. What is the area of parallelogram BFDE?

　　(a) 20

　　(b) 25

　　(c) 50

　　(d) 60

　　(e) 75

Answer:

The easiest way to solve this problem is to notice that we can calculate the area of the parallelogram BFDE by subtracting twice the area of triangle ABE from the area of the square ABCD.

The area of the square ABCD is 10·10 = 100.

The area of triangle ABE is (12)·AB·AE = (12)·10·5 = 25.

In conclusion, the area of parallelogram BFDE is 100 - 2·25 = 50.

延伸阅读：

SAT数学专项练习题（八）

SAT数学专项练习题（九）

SAT数学专项练习题（十一）

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