下面是为大家准备的4道SAT考试数学选择题练习题。同学们在备考SAT数学的过程中，一定要加强习题的练习，熟练到能充分理解题意，争取得到满分。
1.
,
,
, and
are points on a line, with
the midpoint of segment
. The lengths of segments
,
, and
are
,
, and
, respectively. What is the length of segment
?
(A)
(B)
(C)
(D)
(E)
2.In the xy-plane, line 
passes through the points
and
. Line
is perpendicular to line. What is the slope of line
?
(A)
(B)
(C)
(D)
(E)
3.A geologist has
rocks of equal weight. If
rocks and a
-ounce weight balance on a scale with
rocks and a
-ounce weight, what is the weight, in ounces, of one of these rocks?
(A)
(B)
(C)
(D)
(E)
,
,
,
,
, ...
4.The first term of the sequence above is
. Which of the following could be the formula for finding the
term of this sequence for any positive integer
?
(A)
(B)
(C)
(D)
(E)
参考答案及解析：
1.The correct answer is B
Explanation
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
, then
, then
, then
.As you will see, if you try to locate the points in this order, you will be unable to answer the question.
What Is the Question Asking?
The question asks for the length of line segment
. In order to find this length, you have to establish the relative positions of the four points on the line.
What Do You Know?
Try to draw the figure. You might be tempted to locate point
first. Unfortunately, you don't have enough information about
, yet, to place it.
You can place
,
, and
because
is the midpoint of
.
You know the lengths of three of the line segments:
Because you know where
is, you can label the length of
.
Build the Figure, Adding What You Know and What You Can Figure Out
Because
is the midpoint of
, you know that
and
are each
units long.
Where can you place point
?
It has to be
units from
, because
.
It also has to be
units from
, because
.
So the only location for
is between
and
, but closer to
.
Place point
and mark the distances.
It is now an easy matter to figure out the answer to the question:
is
units.
is
units closer to
than
, so
is
units.
