Perimeter, Area, and Surface 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 rug with side 10 ft has perimeter 100 ft.
Corrected: A square rug with side 10 ft has perimeter 40 ft.
100 is the area; perimeter is 4 times 10, which equals 40 feet.
2. Fix the sentence:
A side of 3 m equals 30 cm.
Corrected: A side of 3 m equals 300 cm.
Multiplying 3 by 100 gives 300 centimeters in 3 meters.
3. Fix the sentence:
The perimeter of a triangle with sides 7, 9, and 11 in is 27 sq in.
Corrected: The perimeter of a triangle with sides 7, 9, and 11 in is 27 in.
Perimeter measures distance around, so the unit is inches, not square inches.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A square photo with side 15 cm has area 225 square centimeters.
Fifteen times fifteen equals 225 square centimeters of photo surface.
2. A board is 2 ft long, which equals 24 inches.
Two feet times 12 inches per foot gives 24 inches total.
3. A quadrilateral has sides 6, 8, 10, and 12 m; perimeter is 36 m.
6 plus 8 plus 10 plus 12 equals 36 meters around the shape.
4. A square room has perimeter 32 ft, so each side is 8 ft.
32 divided by 4 equals 8 feet per side of the square.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. A square poster has side 50 cm. Convert this to meters and find the perimeter in meters.
Sample answer: 50 cm equals 0.5 m; perimeter is 4 times 0.5, which is 2 meters.
Each side is 0.5 m, so 4 times 0.5 gives a 2 meter perimeter.
2. An octagonal table has 8 equal sides of 18 inches. What is the perimeter in feet?
Sample answer: 8 times 18 equals 144 inches; 144 divided by 12 equals 12 feet.
144 inches divided by 12 inches per foot equals exactly 12 feet.