This grade 4 lines worksheet answer key solves all 22 problems of the lines, angles, shapes and symmetry worksheet step by step.
Every solution below shows the reasoning step by step, so students can see why an angle is acute or why a figure has a certain number of lines of symmetry. Check each answer, then reread any problem that was missed and look at the figure again.
Grade 4 Lines Worksheet Answer Key: problems 1–5
Problem 1: Name each figure
(a) Two endpoints, so it is a line segment. (b) One endpoint and an arrow, so it is a ray. (c) Arrows on both ends and no endpoints, so it is a line. (d) A single dot is a point.
Problem 2: Count the endpoints
(a) The beam starts at one point and goes on forever, so it is a ray with 1 endpoint. (b) The ruler edge stops at both ends, so it is a line segment with 2 endpoints. (c) The road goes on forever both ways, so it is a line with 0 endpoints.
Problem 3: Segments on a line
Pair the points: A and B, B and C, A and C. That makes 3 pairs.
The segments are \(\overline{AB}\), \(\overline{BC}\) and \(\overline{AC}\). 3 line segments
Problem 4: Classify the angles
(a) It is smaller than a square corner: acute. (b) The square mark shows a square corner: right. (c) It is wider than a square corner but not a straight line: obtuse.
Problem 5: Clock angles
At 3:00 the hands make a square corner: right. At 2:00 the hour hand is closer to 12, so the angle is smaller than a square corner: acute. At 5:00 the hour hand is past the 3, so the angle is wider than a square corner: obtuse.
Grade 4 Lines Worksheet Answer Key: problems 6–10
Problem 6: Angles around us
- A paper corner is a square corner: right.
- Barely open is smaller than a square corner: acute.
- Tilted far back is wider than a square corner: obtuse.
Problem 7: Parallel or perpendicular
(a) The lines cross at a slant, with no square corner: neither. (b) The lines never meet: parallel. (c) The lines cross at a square corner: perpendicular.
Problem 8: Street map
Oak Street and Pine Street never meet, so they are parallel. Main Street crosses each at a square corner, so Main Street is perpendicular to Oak Street, and also perpendicular to Pine Street.
Problem 9: Classify the triangles
(a) One angle is a square corner: right triangle. (b) One angle is wider than a square corner: obtuse triangle. (c) All three angles are smaller than a square corner: acute triangle.
Problem 10: Pairs of parallel sides
(a) Top and bottom are parallel, and the slanted sides are parallel: 2 pairs. (b) Only the top and bottom are parallel: 1 pair. (c) No sides stay the same distance apart: 0 pairs.
Grade 4 Lines Worksheet Answer Key: problems 11–15
Problem 11: Count right angles
(a) A rectangle has square corners at all four vertices: 4. (b) Only the two corners on the left are square: 2. (c) A slanted parallelogram has no square corners: 0.
Problem 12: Lines of symmetry
(a) The rectangle folds lengthwise and crosswise: 2. (b) The triangle folds down the middle: 1. (c) The parallelogram has no fold that matches: 0. (d) The square folds two ways through the sides and two ways corner to corner: 4.
Problem 13: True or false
- False. A ray has one endpoint.
- True.
- False. Parallel lines never meet.
- False. An obtuse angle is larger than a right angle.
Problem 14: Finish the shape
Each point on the left side is the same distance from the dashed line as the matching point on the right. The right side is 3 squares wide, so the left side is also 3 squares wide, with a matching notch in the top: 1 square wide, 1 square deep, and 1 square away from the dashed line.
Problem 15: Square and rectangle
Yes. A rectangle has 4 square corners and 2 pairs of parallel sides. A square also has 4 square corners, and each side is parallel to the opposite side, so it has 2 pairs too. Jamal is right.
Grade 4 Lines Worksheet Answer Key: problems 16–20
Problem 16: Letters with symmetry
H folds two ways, up and down and left and right: 2. A folds down the middle: 1. E folds across the middle (top half matches bottom half): 1. Z has no fold that matches: 0.
Problem 17: Flag stripes
Flag A: the top and bottom stripes are both red, so the horizontal fold works. The vertical fold also works because every stripe is the same color across. That is 2 lines of symmetry.
Flag B: the vertical fold works, but folding top onto bottom puts red on blue. That is 1 line of symmetry.
Problem 18: Quadrilateral PQRS
PS is perpendicular to PQ, so the angle at P is a right angle. PS is also perpendicular to SR, so the angle at S is a right angle. Side QR slants, so the angles at Q and R are not square corners.
That is 2 right angles and 1 pair of parallel sides (PQ and SR). The figure is a trapezoid.
Problem 19: Sandwich cut
(a) Each piece keeps one square corner of the sandwich, and its other two angles are smaller than a square corner. Each piece is a right triangle.
(b) The square has 4 lines of symmetry: 2 through the middles of opposite sides and 2 through opposite corners. 4 lines
Problem 20: Road signs
The stop sign has 8 equal sides, so it has 8 lines of symmetry. The yield sign has 3 equal sides, so it has 3. The house-shaped school sign has 1, straight down the middle.
Stop: 8, yield: 3, school: 1.
Grade 4 Lines Worksheet Answer Key: problems 21–22
Problem 21: Skateboard ramp
The wall is perpendicular to the ground, so the angle where they meet is a right angle. A triangle with one right angle is a right triangle.
The other two angles are smaller than a square corner, so 2 angles are acute.
Problem 22: Mei's mystery shape
(a) Two pairs of parallel sides with no square corners make a parallelogram.
(b) Four right angles and two pairs of parallel sides make a rectangle.
How to use this grade 4 lines worksheet answer key
Read this grade 4 lines worksheet answer key after trying each problem yourself, and redo any problem you missed.
See every chapter on the Grade 4 math page.