Classifying Quadrilaterals — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A rhombus have four congruent sides in Grade 4 geometry.
Corrected: A rhombus has four congruent sides in Grade 4 geometry.
Grade 4 grammar uses 'has' with singular subjects; the math fact stays the same: four congruent sides.
2. Fix the sentence:
Every rhombus are a square with four right angles.
Corrected: Not every rhombus is a square with four right angles.
A rhombus needs four congruent sides but not right angles; only when all angles are right is it a square.
3. Fix the sentence:
The diagonals of a rhombus bisects each other at right angles.
Corrected: The diagonals of a rhombus bisect each other at right angles.
Grade 4 grammar pairs plural subjects with plural verbs; the math attribute is that rhombus diagonals are perpendicular.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A Grade 4 rhombus has four congruent sides.
Rhombuses are quadrilaterals whose four sides are all equal in length.
2. A rhombus looks like a tilted square because its angles can lean.
Grade 4 students compare a rhombus to a tilted square: equal sides, but angles are not always right angles.
3. A square is a special rhombus that also has four right angles.
Every square is a rhombus, but only a rhombus with four right angles can be called a square in Grade 4.
4. The diagonals of a rhombus bisect each other at the center.
Grade 4 vocabulary 'bisect' means cut in half; rhombus diagonals bisect each other and meet at right angles.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Explain how a rhombus is similar to and different from a square in Grade 4 classification.
Sample answer: A rhombus and a square both have four congruent sides. They are different because a square also has four right angles, while a rhombus may have angles that are not 90 degrees.
Grade 4 hierarchy: every square is a rhombus, but not every rhombus is a square.
2. Describe two attributes you would check to confirm a shape is a rhombus in Grade 4 geometry.
Sample answer: First I would check that all four sides are congruent. Then I would check that opposite sides are parallel, since a rhombus is also a parallelogram with equal sides.
A rhombus is defined by congruent sides plus the parallelogram property of two pairs of parallel sides.