2016年1月13日SAT数学题
In the x y-plane, line l passes through the points (a,0) and (0,2a), where a > 1. What is the slope of line l?
(A) -2
(B) -1/2
(C) 2
(D) -2a
(E) 2a
解释：
Choice (A) is correct. Given two points on a line, the slope of the line can be found by dividing the change in the y-coordinates between the points by the corresponding change in the x-coordinates. Hence, since line l passes through the points (a,0) and (0,2a), its slope is change in y-coordinates/change in x-coordinates = ((2a)-0)/(0-a) = (2a)/-a = -2.
以上就是2016年1月13日的SAT数学题，正确答案是A。
2016年1月28日SAT数学题
If a, b, and c are numbers such that a/ b = 3 and b/ c = 7, then (a+b)/ (b+c) is equal to which of the following?
(A) 7/2
(B) 7/8
(C) 3/7
(D) 1/7
(E) 21
解释：
From a/b = 3 is implied that (a+b)/b = 4 (1)
And from b/c = 7 is implied that b/(b+c) = 7/8 (2)
If we multiply (1) and (2) together, we have that (a+b)/(b+c) = 4*(7/8) = 7/2 (b is canceled out).
以上就是2016年1月28日的SAT数学题，正确答案是A。
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