Circumference from the area — Mensuration Aptitude Question
Circumference from the area: The area of a circle is 154 cm². What is its circumference? (Take π = 22/7.) Answer and worked solution on CodeKairo.
- Topic: Mensuration
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 60 seconds
Question
The area of a circle is 154 cm². What is its circumference? (Take π = 22/7.)
Options
- 22 cm
- 33 cm
- 44 cm
- 55 cm
Show the answer and the worked solution
Correct answer: C. 44 cm
Worked solution
- (22/7)r² = 154 → r² = 49 → r = 7 cm.
- Circumference = 2 × (22/7) × 7 = 44 cm.
Answer: 44 cm.
The idea
Route through the radius: area gives r, and r gives the circumference. The pair r = 7, area 154, circumference 44 is worth memorising.
Shortcut. Once r = 7, circumference = 2 × area ÷ r = 2 × 154 ÷ 7 = 44 cm.
Common trap. 22 cm — computing πr (22/7 × 7) and forgetting the 2 in 2πr; that is only half the circle.