Question

calculate the curcumference of a circle that has

a) a radius of 7cm
b) a radius of 56cm
c) a diameter of 9.3cm
d) a diameter of 98mm

give answer correct to two decimal place


use
$\pi$
=
$\frac{22}{7}$


​

Answer 1

Answer:

The Formula to find the circumference = 2πr.

a) A radius of 7 cm.

Hence, 2πr = 2 × 22/7 ×7 = 44 cm.

b) A radius of 56 cm

Hence, 2πr = 2 × 22/7 × 56 = 2 × 22 × 8 = 352 cm.

c) A diameter of 9.3 cm

Hence, 2πr = 2 × 22/7 × 93/20

= 22/7 × 93/10

= 11/7 × 93/5

= 1023/35

= 29.22 cm

d) A diameter of 98 mm

Hence, 2πr = 2 × 22//7 × 98/2

= 2 × 22 × 14/2

= 2 × 11 × 14

= 308 mm

---------------------------------

• Area of a circle = πr²
• Circle is a locus of infinite points located at a distance from a fixed point called the centre.
• Perimeter of a square = 4s
• Perimeter of a rectangle = 2( l + b )
• Area of a square = s²
• Area of a rectangle = lb

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Answer 2

a) radius of a circle 7cm

Circumference of a circle=2πr

=2×(22/7)×7cm=44cm

b) radius of a circle 56cm

Circumference of a circle=2πr

=2×(22/7)×56cm=352cm

c) diameter of a circle 9.3cm

radius=9.3/2=4.65cm

Circumference of a circle=2πr =2×(22/7)×4.65cm=(204.6/7)cm=29.22cm ( appr.)

d) diameter of a circle 98mm

radius=98/2=49mm

Circumference of a circle=2πr

=2×(22/7)×49mm=308mm