Problem 1 :
The circumference of circle whose diameter is 14 cm will be ________.
Solution :
Given, diameter = 14 cm
Radius r = 14/2 = 7 cm
Circumference = 2πr
= 2 × 22/7 × 7
= 44 cm
So, the circumference of circle whose diameter is 14 cm will be 44 cm.
Problem 2 :
What is the circumference of a circular disc of radius 14 cm?
Solution :
Given, Radius r = 14 cm
Circumference = 2πr
= 2 × 22/7 × 14
= 88 cm
So, the circumference of a circular disc is 88 cm.
Problem 3 :
The circumference of a circle is 31.4 cm. find the radius. (Take π = 3.14)
Solution :
Given, circumference of the circle = 31.4 cm
2πr = 31.4
2 × 3.14 × r = 31.4
6.28 × r = 31.4
r = 31.4/6.28
r = 5 cm
So, radius of the circle is 5 cm.
Problem 4 :
If the circumference of a circle with radius 3.5 cm is 22 cm. Find the perimeter of the semicircle. (Take π = 3.14)
Solution :
Circumference = 22 cm
Radius r = 3.5 cm
Perimeter of the semicircle = πr + 2r
= r (π + 2)
= 3.5 (3.14 + 2)
= 3.5 ×5.14
= 17.99 cm
So, perimeter of the semicircle is 17.99 cm.
Problem 5 :
If the circumference of a circle is 132 cm. Find the perimeter of the semicircle. (Take π = 3.14)
Solution :
Circumference of a circle = 132 cm
2πr = 132
r = 132/2π
r = 132/ (2 × 3.14)
r = 132/6.28
r = 21.01 cm
Perimeter of the semicircle = πr + 2r
= r (π + 2)
= 21.01 (3.14 + 2)
= 21.01 × 5.14
= 107.99 cm
= 108 cm
So, perimeter of the semicircle is 108 cm.
Problem 6 :
The radii of two circles are in the ratio 2: 3. What is the ratio of their circumference?
Solution :
Let the radius of two circle be 2x and 3x respectively.
Circumference of a circle = 2πr
Circumference of first circle = 2 × π × 2x
= 4πx
Circumference of second circle = 2 × π × 3x
= 6πx
Ratio of circumference of two circles = 4πx/6πx
= 4/6
= 2/3
Hence, ratio of their circumference is 2: 3.
Problem 7 :
A 44 m long wire is bent to form a circle. Find the diameter of the circle.
Solution :
Given, length of the wire = 44 cm
Circumference of the circle = length of the wire = 44 cm
2πr = 44
2 × 22/7 × r = 44
r = 44 × 7/44
r = 7 cm
Diameter = 2 × radius
= 2 × 7
Diameter = 14 cm
So, the diameter of the circle is 14 cm.
Problem 8 :
A wire is in the form of a circle of radius 35 m. It is now bent in the form of an equilateral triangle. Find the side of the triangle.
Solution :
Given, the radius of the circle = 35 m
Circumference of circle = 2πr
= 2 × 22/7 × 35
= 220 m
The circumference of circle = perimeter of equilateral triangle
Let, one side of an equilateral triangle be x.
Perimeter of equilateral triangle = 3x
3x = 220
x = 220/3
x = 73.33 m
So, the each side of an equilateral triangle is 73.33 m.
May 21, 24 08:51 PM
May 21, 24 08:51 AM
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