All SAT Math Resources
Example Questions
Example Question #1 : Circles
Two chords of a circle, and
, intersect at a point
.
is twice as long as
,
, and
.
Give the length of .
Insufficient information is given to find the length of .
Insufficient information is given to find the length of .
Let stand for the length of
; then the length of
is twice this, or
. The figure referenced is below:
If two chords intersect inside the circle, then they cut each other in such a way that the product of the lengths of the parts is the same for the two chords - that is,
Substituting the appropriate quantities, then solving for :
This statement is identically true. Therefore, without further information, we cannot determine the value of - the length of
.
Example Question #1 : Circles
Two chords of a circle, and
, intersect at a point
.
is 12 units longer than
,
, and
.
Give the length of (nearest tenth, if applicable)
Let stand for the length of
; then the length of
is
. The figure referenced is below:
If two chords intersect inside the circle, then they cut each other in such a way that the product of the lengths of the parts is the same for the two chords - that is,
Substituting the appropriate quantities, then solving for :
This quadratic equation can be solved by completing the square; since the coefficient of is 12, the square can be completed by adding
to both sides:
Restate the trinomial as the square of a binomial:
Take the square root of both sides:
or
Either
,
in which case
,
or
in which case
,
Since is a length, we throw out the negative value; it follows that
, the correct length of
.
Example Question #1 : Chords
A diameter of a circle is perpendicular to a chord
at a point
.
What is the diameter of the circle?
Insufficient information is given to answer the question.
In a circle, a diameter perpendicular to a chord bisects the chord. This makes the midpoint of
; consequently,
.
The figure referenced is below:
If two chords intersect inside the circle, then they cut each other in such a way that the product of the lengths of the parts is the same for the two chords - that is,
Setting , and solving for
:
,
the correct length.
Example Question #1 : Circles
Two chords of a circle, and
, intersect at a point
.
Give the length of .
Insufficient information is given to answer the question.
Let , in which case
; the figure referenced is below (not drawn to scale).
If two chords intersect inside the circle, then they cut each other in such a way that the product of the lengths of the parts is the same for the two chords - that is,
Setting , and solving for
:
,
which is the length of .
Example Question #2 : Circles
A diameter of a circle is perpendicular to a chord
at point
.
and
. Give the length of
(nearest tenth, if applicable).
insufficient information is given to determine the length of .
A diameter of a circle perpendicular to a chord bisects the chord. Therefore, the point of intersection is the midpoint of
, and
.
Let stand for the common length of
and
,
The figure referenced is below.
If two chords intersect inside the circle, then they cut each other in such a way that the product of the lengths of the parts is the same for the two chords - that is,
Set and
, and
; substitute and solve for
:
This is the length of ; the length of
is twice this, so
Example Question #251 : Geometry
Figure is not drawn to scale
In the provided diagram, the ratio of the length of to that of
is 7 to 2. Evaluate the measure of
.
Cannot be determined
Cannot be determined
The measure of the angle formed by the two secants to the circle from a point outside the circle is equal to half the difference of the two arcs they intercept; that is,
The ratio of the degree measure of to that of
is that of their lengths, which is 7 to 2. Therefore,
Letting :
Therefore, in terms of :
Without further information, however, we cannot determine the value of or that of
. Therefore, the given information is insufficient.
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