Perimeter and Area — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A square with 4 cm sides has a perimeter of 12 cm.
Corrected: A square with 4 cm sides has a perimeter of 16 cm.
All four sides of a square are equal, so 4 + 4 + 4 + 4 = 16 cm, not 12. The sentence should say 16 cm because every side counts.
2. Fix the sentence:
A rectangle 5 cm by 3 cm has an area of 8 square cm.
Corrected: A rectangle 5 cm by 3 cm has an area of 15 square cm.
Area uses multiplication: 5 × 3 = 15 square cm, not 8. The rectangle holds 15 unit squares inside, so 15 is the correct area.
3. Fix the sentence:
The area of a rectangle is 24 cm.
Corrected: The area of a rectangle is 24 square cm.
Area is measured in square units because it counts how many 1-by-1 squares fit inside. Writing just cm leaves out the word that shows we are talking about flat space.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A rectangle is 8 cm long and 2 cm wide. Its area is 16 square cm.
Multiplying 8 × 2 = 16 gives 16 square cm of area. Picture two rows of 8 little squares stacked together to fill the rectangle.
2. Area tells how many square units cover a flat surface.
Square units are 1-by-1 boxes that tile a flat surface, so area always counts square units. That is why the answer fits the sentence.
3. A rectangle with sides 3 m and 6 m has a perimeter of 18 m.
Perimeter is 3 + 6 + 3 + 6 = 18 m around the edge. The two short sides total 6 and the two long sides total 12, making 18.
4. A square with 5 cm sides has a perimeter of 20 cm.
A square's four sides are all the same, so 5 × 4 = 20 cm goes all the way around. Adding 5 + 5 + 5 + 5 gives the same 20.
Part C: True or False?
Read each statement. Circle True or False.
1. A square with 4 cm sides has an area of 16 square cm.
True False
True. Each side measures 4 cm, so 4 × 4 = 16 square cm covers the inside of the square.
2. Perimeter measures the space inside a shape.
True False
False. Perimeter measures the distance around the outside; the space inside is called area.
3. A rectangle with sides 9 cm and 1 cm has a perimeter of 20 cm.
True False
True. Adding 9 + 1 + 9 + 1 = 20 cm gives the perimeter, since opposite sides of a rectangle are equal.