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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

A, B, C, and D are points on a line, with D the midpoint of segment B C. The lengths of segments A B, A C, and B C are 10, 2, and 12, respectively. What is the length of segment A D?

(A) 2
(B) 4
(C) 6
(D) 10
(E) 12

答案和解析

答案：B

解析：

The key to this question lies in not jumping to incorrect conclusions. The question names the points on a line. It gives you a variety of information about the points. The one thing it does not do is tell you the order in which the points fall.

Many students assume that the order of the points is A, then B, then C, then D. As you will see, if you try to locate the points in this order, you will be unable to answer the question.