Question

The circumference of the semicircle with diameter 20 cm is

Answer 1

Heya,  

Diameter = 20cm

Radius = 20/2 cm = 10cm  

We know,

Circumference of Semi-circle = r(π + 2)  

∴ Circumference of Semi-Circle  

= 10(22/7 + 2) cm

= 10(22 + 14/7) cm

= 10(36/7)cm

= 360/7 cm  

Hope it helps !

Answer 2

Hey there ! Thanks for the question!

Circumference of the circle is the length of path around it. Or the distance you need to travel if you start from one point of the circle and reach the point again.

To travel around the circle, You need to travel 2πr or πd units, where r is the radius of the circle.

When you travel around a semi circle you need to travel half the circumference of circle and travel through diameter too.

So , Circumference of semicircle = πr + 2r

Here We don't have radius, So let's express the formula in terms of diameter.

Circumference of semi circle = πd/2 + d =1/2 ( πd + 2d ) = 1/2d ( π + 2 )

Given diameter = 20 cm.

Circumference of semi circle = 1/2 ( 20 ) ( π + 2 )

= 10 ( π + 2 )

= 10 ( 22/7 + 2 )

= 10 ( 22 + 14 / 7 )

= 10( 36)/7

= 360/7 cm

or

= 10 ( 3.14 + 2 )

= 10 ( 5.14 )

= 51.4 cm

Therefore, The diameter of the circle is 360/7 cm or 51.4cm.