The area of a circle is 154 cm². What is its diameter? (Take π = 227)
- 7 cm
- 14 cm
- 22 cm
- 49 cm
Need a hint?
Area ÷ π gives radius × radius. Which number times itself gives that?
Worked answer
- Radius × radius = 154 ÷ 22/7 = 154 × 7/22 = 49.
- 7 × 7 = 49, so the radius is 7 cm.
- Diameter = 2 × 7 = 14 cm.
Answer: 14 cm
The mistake this question tests
Habit
Radius and diameter in circles
7 cm is the radius. The question asks for the diameter, which is twice the radius.
How to fix it at home →Wrong answers children often give:
- 7 cm Radius and diameter in circles
- 49 cm Calculation slip
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