The length of an arc is 12cm, and the center angle of the circle it faces is 270 degrees. How many centimeters is the circumference of the circle where the arc is located?

The length of an arc is 12cm, and the center angle of the circle it faces is 270 degrees. How many centimeters is the circumference of the circle where the arc is located?

Arc length: center angle = circumference of the circle: 360 degree
The circumference of the circle = the length of the arc X360 °
=12x360÷270
=16（cm）

If the two arc lengths of a and B are equal and the central angle of a is twice that of B, the ratio of the circumference of a circle to that of B circle is ()

It shows that radius a is half of radius B
The perimeter ratio is 1:2

It is known that the circumference of a circle is 30cm, then the arc length to which the central angle of 120 ° is directed is

30x120/360
=10 cm