All SSAT Upper Level Math Resources
Example Questions
Example Question #11 : How To Find Whether Lines Are Perpendicular
Lines 1 and 2, which are perpendicular, have their -intercepts at the point . The -intercept of Line 1 is at the point . Give the -intercept of Line 2.
The slope of a line with -intercept and -intercept is . For Line 1, , so Line 1 has slope . The slope of Line 2, which is perpendicular to Line 1, will be the opposite of the reciprocal of this, which is . Setting equal to this and , we get
, or
Cross-multiplying:
The -intercept of Line 2 is .
Example Question #12 : How To Find Whether Lines Are Perpendicular
Which of the following choices gives the equations of a pair of perpendicular lines with the same -intercept?
and
and
and
and
and
and
All of the equations are given in slope-intercept form , so we can answer this question by examining the coefficients of , which are the slopes, and the constants, which are the -intercepts. In each case, since the lines are perpendicular, each -coefficient must be the other's opposite reciprocal, and since the lines have the same -intercept, the constants must be equal.
Of the five pairs, only
and
and
and
have equations whose -coefficients are the other's opposite reciprocal. Of these, only the latter pair of equations have equal constant terms.
and
is the correct choice.
Example Question #13 : How To Find Whether Lines Are Perpendicular
Given: the following three lines on the coordinate plane:
Line 1: The line of the equation
Line 2: The line of the equation
Line 3: The line of the equation
Which of the following is a true statement?
None of the other responses is correct.
No two of Line 1, Line 2, or Line 3 form a pair of perpendicular lines.
Line 1 and Line 3 are perpendicular; Line 2 is perpendicular to neither.
Line 2 and Line 3 are perpendicular; Line 1 is perpendicular to neither.
Line 1 and Line 2 are perpendicular; Line 3 is perpendicular to neither.
Line 1 and Line 3 are perpendicular; Line 2 is perpendicular to neither.
The slope of each line can be calculated by putting the equation in slope-intercept form and noting the coefficient of :
Line 1:
Slope of Line 1:
Line 2:
Slope of Line 2:
Line 3: The equation is already in slope-intercept form; its slope is 2.
Two lines are perpendicular if and only their slopes have product . The slopes of Lines 1 and 3 have product ; they are perpendicular. The slopes of Lines 1 and 2 have product ; they are not perpendicular. The slopes of Lines 2 and 3 have product ; they are not perpendicular.
Correct response: Line 1 and Line 3 are perpendicular; Line 2 is perpendicular to neither.
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