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 rectangle with sides 5 cm and 3 cm has a perimeter of 15 cm.
Corrected: A rectangle with sides 5 cm and 3 cm has a perimeter of 16 cm.
Perimeter adds every side once: 5 + 3 + 5 + 3 = 16 cm, not 15. The original sentence forgot one of the matching sides, so 16 cm is the right total.
2. Fix the sentence:
A rectangle that is 4 units long and 2 units wide has an area of 6 square units.
Corrected: A rectangle that is 4 units long and 2 units wide has an area of 8 square units.
Area is found by multiplying length and width: 4 × 2 = 8 square units. The sentence should say 8, not 6, because 4 rows of 2 squares fill the rectangle.
3. Fix the sentence:
The perimeter of a shape is measured in square centimeters.
Corrected: The perimeter of a shape is measured in centimeters.
Perimeter is a length around a shape, so it is measured in centimeters, not square centimeters. Square units are reserved for area, which counts the space inside.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A rectangle has sides of 6 cm and 4 cm. Its perimeter is 20 cm.
Going around the rectangle once means 6 + 4 + 6 + 4 = 20 cm. The two long sides add to 12 and the two short sides add to 8, making 20.
2. A rectangle is 3 units long and 5 units wide. Its area is 15 square units.
Area is rows times columns of unit squares: 3 × 5 = 15 square units. The rectangle holds 15 little squares inside.
3. To find the perimeter of a shape, you add all the side lengths.
Perimeter is the total distance around a shape, so you add all the side lengths together. Adding gives one number that tells how far the edge stretches.
4. A square with sides of 7 cm has a perimeter of 28 cm.
A square has four equal sides, so 7 + 7 + 7 + 7 = 28 cm, which is the same as 4 × 7. All sides matching is what makes the math so simple.
Part C: True or False?
Read each statement. Circle True or False.
1. A rectangle that is 6 units long and 3 units wide has an area of 18 square units.
True False
True. Multiplying 6 × 3 = 18, so 18 unit squares fit inside the rectangle and that is the area.
2. Perimeter is measured in square units.
True False
False. Perimeter is a length around a shape, so it uses regular units like cm or inches; square units belong to area instead.
3. A rectangle with sides 2 cm and 5 cm has a perimeter of 14 cm.
True False
True. Adding 2 + 5 + 2 + 5 = 14 cm, which is the perimeter of a rectangle whose opposite sides match.