Line graph questions ask you to compare line segments on a coordinate grid. The key is to calculate gradients carefully, then use the rules for parallel lines, perpendicular lines, translations, and missing coordinates.
For students who can read plotted points, but lose marks using gradients, parallel lines, perpendicular lines, and translations.
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The papers focus on coordinate line segments: finding gradients, comparing parallel lines, checking perpendicular lines, translating a line, and using a known gradient to find a missing coordinate.
Subtract the y-values, then divide by the change in x-values.
Example: From (3, 4) to (6, 2), gradient = 2 - 46 - 3 = -23.
If two line segments have equal gradients, they are parallel.
Example: A line with gradient -12 is parallel to any other line with gradient -12.
For a perpendicular line, flip the fraction and change the sign.
Example: A line with gradient -1 has perpendicular gradient 1.
Apply the same change to both coordinates of both endpoints.
Example: Moving (5, 1) and (7, 2) two left and one up gives (3, 2) and (5, 3).
Three useful moves: calculate the gradient, compare it with each option, and watch for translations or missing coordinate traps.
Question: Which line is parallel to the line from (3, 4) to (6, 2)?
Step 1: Gradient = 2 - 46 - 3 = -23.
Step 2: A parallel line must also have gradient -23.
Tip: Check each option by calculating its gradient, not by judging the drawing by eye.
Question: Which option shows the same line from (5, 1) to (7, 2) moved 2 squares left and 1 square up?
Step 1: A move 2 left and 1 up means x - 2 and y + 1.
Step 2: (5, 1) becomes (3, 2).
Step 3: (7, 2) becomes (5, 3).
Tip: Translate both endpoints. Moving only one endpoint changes the gradient.
Question: A second line joins (2, 5) to (6, y). If it is parallel to a line from (3, 1) to (7, 2), what is y?
Step 1: Gradient of the first line = 2 - 17 - 3 = 14.
Step 2: The second line must also have gradient 14.
Step 3: Its run is 6 - 2 = 4, so the rise must be 1.
Tip: y = 5 + 1 = 6.
Want to check the level and layout first? Download the free 3-question sample. It uses the same question style, printable format, and answer-key approach as the full pack.
Download Free Sample PDFThe full Line Graphs pack contains 90 questions across 3 printable test sets. Students practise gradients, parallel lines, perpendicular lines, missing coordinates, translations, and line relationships.
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