Perimeter of polygons: Class 6 practice
Perimeter is the total length around a shape. Read the method, follow the three worked examples, then try the six questions.
What you should know first
- Addition
- Polygons
The idea behind perimeter of polygons
Perimeter is the total length around a shape. For a regular polygon with n equal sides, P = n × side. For irregular shapes add every side, finding missing ones first.
Step-by-step method
- List every side length.
- For a regular polygon multiply side × number of sides.
- Find missing sides from given totals.
Worked example 1 (Basic)
Find the perimeter of a regular triangle of side 25 cm.
- P = 3 × 25
- = 75 cm
- Answer: 75 cm
Worked example 2 (Standard)
A regular decagon has perimeter 250 cm. Find each side.
- side = 250 ÷ 10
- = 25 cm
- Answer: 25 cm
Worked example 3 (Challenge)
A quadrilateral has perimeter 27 cm and three sides 10, 4 and 4 cm. Find the fourth.
- 27 − (10 + 4 + 4)
- = 9 cm
- Answer: 9 cm
Common mistakes and misconceptions
- Missing a side
- Mixing units
Practice questions
- (Basic) Find the perimeter of a regular square of side 19 cm.
- (Basic) Find the perimeter of a regular decagon of side 5 cm.
- (Standard) A regular triangle has perimeter 72 cm. Find each side.
- (Standard) A regular triangle has perimeter 36 cm. Find each side.
- (Challenge) A quadrilateral has perimeter 29 cm and three sides 5, 6 and 4 cm. Find the fourth.
- (Challenge) A quadrilateral has perimeter 47 cm and three sides 7, 10 and 15 cm. Find the fourth.
Answer key with full working
- Q1: P = 4 × 19 → = 76 cm → Answer: 76 cm
- Q2: P = 10 × 5 → = 50 cm → Answer: 50 cm
- Q3: side = 72 ÷ 3 → = 24 cm → Answer: 24 cm
- Q4: side = 36 ÷ 3 → = 12 cm → Answer: 12 cm
- Q5: 29 − (5 + 6 + 4) → = 14 cm → Answer: 14 cm
- Q6: 47 − (7 + 10 + 15) → = 15 cm → Answer: 15 cm
Syllabus note
This skill is listed under "Mensuration" for Class 6 in the NCERT/CBSE books. ICSE, IGCSE, IB and state boards may teach it in a different chapter or year.
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.
Related practice and notes
Frequently asked questions
Which chapter is perimeter of polygons in?
"Mensuration", Class 6 Maths (NCERT/CBSE). Other boards may place it differently.
How were the answers checked?
Answers on this page are generated and automatically re-checked by a second, independent calculation. They have not been reviewed by a teacher — if you spot a problem, tell us on WhatsApp.