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4th grade

Course: 4th grade > Unit 11

Lesson 6: Line of symmetry
Math
4th grade
Plane figures
Line of symmetry
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Symmetry review

CCSS.Math:
4.G.A.3
Google Classroom
Review symmetrical shapes and lines of symmetry.  Then, try some practice problems.

Line of symmetry

A start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 is a line where we can fold the image and have both halves match exactly.
Example:
When we divide the figure with Line start color #1fab54, A, end color #1fab54, the resulting two parts are mirror images of each other:
An isosceles triangle with a line labeled A that passes through the vertex joining the equal length sides to the center of the third side.
Line start color #1fab54, A, end color #1fab54 is a line of symmetry.
Want to learn more about lines of symmetry? Check out this video.

Symmetrical figures

Shapes are start color #aa87ff, start text, s, y, m, m, e, t, r, i, c, a, l, end text, end color #aa87ff if they have at least one start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 on them.
Example:
This shape is start color #aa87ff, start text, s, y, m, m, e, t, r, i, c, a, l, end text, end color #aa87ff:
A shape with five sides of equal lengths and all equal angles.
Because we can draw at least one start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 on it:
The same five-sided shape with five lines of symmetry, each cutting it in half through the center point.
Want to learn more about symmetrical figures? Check out this video.

Practice

Problem 1
  • Current
In the figure below, which of the following is a line of symmetry?
Choose all answers that apply:
A four-sided shape where the left and right vertical sides are parallel, but the top and bottom sides are not parallel. The right side is longer than the left side. The top side moves up and to the right while the bottom side moves down and to the right. The shape is divided by three lines labeled A, B, and C. Line A is a horizontal line that divides the top and bottom half evenly so when folded, the top and bottom sides match. Line B divides the left and right half evenly, but when folded, both sides do not match. Line C passes through the top left corner and bottom right corner, but is not evenly divided.

Want to try more problems like this? Check out these exercises:
Identify lines of symmetry and symmetrical figures
Draw lines of symmetry and symmetrical figures

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