Find the the circumference of a circle whose area is 4 times area of a circle with diameter 21 CM
Answers
Given:
Diameter of a circle = 21 cm.
→ Radius of the circle = 21/2 cm
Find:
circumference
Solution:
Area of other circle = 4 * area of the circle.
We know that,
Area of a circle with radius r is :
→ πr²
Let the radius of the given circle be r₁ and radius of the other circle be r₂
Hence,
→ π * (r₂)² = 4 * π * (r₁)²
Putting the value of r₁ and cancelling π from both sides we get,
→ (r₂)² = 4 * (21/2)²
→ (r₂)² = 4 * (21)²/4
→ (r₂)² = (21)² cm
→ r₂ = 21 cm
[If powers are equal, then the bases are also equal ]
Now,
Circumference of a circle = 2πr
→ Circumference of the other circle = 2 * π * r₂
→ Circumference of the other circle = 2 * 22/7 * 21
→ Circumference of the other circle = 132 cm
Hence, the circumference of the other circle is 132 cm.
I hope it will help you.
Regards.
Answer:
→ (r₂)² = 4 * (21/2)²
→ (r₂)² = 4 * (21)²/4
→ (r₂)² = (21)² cm
→ r₂ = 21 cm
[If powers are equal, then the bases are also equal ]
Now,
Circumference of a circle = 2πr
→ Circumference of the other circle = 2 * π * r₂
→ Circumference of the other circle = 2 * 22/7 * 21
→ Circumference of the other circle = 132 cm
Step-by-step explanation: