In a rectangular coordinate system, which of the following points is intersected by the line connected by the coordinates (5,6) and (21,18)?
A. (9,9)
B. (12,12)
C. (13,13)
D. (12,13)
E. (16,15)
OA is A.
In this PS question, what is faster? make the graph or use the equation of a line? what is the best way to solve it?
In a rectangular coordinate system...
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- Brent@GMATPrepNow
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One approach is to first find the slopeVincen wrote:In a rectangular coordinate system, which of the following points is intersected by the line connected by the coordinates (5,6) and (21,18)?
A. (9,9)
B. (12,12)
C. (13,13)
D. (12,13)
E. (16,15)
Slope = (18 - 6)/(21 - 5) = 12/16 = 3/4
IMPORTANT: if the slope is 3/4, then we can start at (5,6) and move up 3 spaces and then move right 4 spaces to find other points on the line (with INTEGER values)
Start at: (5,6)
Move 3 units up and 4 units to the right to get to the point (9,9) (check answer choices - it's there!)
Answer: A
Cheers ,
Brent
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- Jeff@TargetTestPrep
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Let's first create the equation of a line for coordinates (5,6) and (21,18).Vincen wrote:In a rectangular coordinate system, which of the following points is intersected by the line connected by the coordinates (5,6) and (21,18)?
A. (9,9)
B. (12,12)
C. (13,13)
D. (12,13)
E. (16,15)
Slope = change in y/change in x = 12/16 = 3/4.
We can substitute in either ordered pair to calculate the y-intercept. Let's use (5,6):
y = (3/4)x + b
6 = (3/4)(5) + b
6 = 15/4 + b
24/4 = 15/4 + b
9/4 = b
Thus, y = (3/4)x + 9/4
Let's now substitute each set of coordinates to see which holds true in our equation.
A) (9,9)
9 = (3/4)(9) + 9/4 ?
9 = 27/4 + 9/4 ?
9 = 36/4 ?
9 = 9 ? ..... Yes!
Answer: A
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