A 4 mm circle would have a diameter of 4 millimeters, meaning the distance across the circle passing through its center would be 4 mm. This circle would be relatively small, about the size of a standard pencil eraser. In terms of area, the circle would cover approximately 12.57 square millimeters.
I'm wondering what the original, or book, question actually asks, but in this case, a it is a circle larger in radius, diameter and circumference by the ratio 4:3; and in area by the ratio 16:9.
By unit of length and distance and conversion ,we can say that 1 mm=0.1 cm 4 mm=0.4cm
Circumference = 2*pi*4 mm or 8*pi mm
27.2 mm
Diameter of circle: 13/pi = 4 mm rounded to the nearest integer
A circle with a diameter of 4 mm has an area of : 12.57 mm2
46.5 millimeters is 1.83 inches.
4/16 = 1/4. This may seem a tautological description but : it looks like a quarter of a circle.
You neglected to say whether the 4mm is the radius of the circle, or the diameter,or the circumference. Each possibility gives you a different area.
It could resemble a pie with roughly 1/4 of it missing.
It looks like 3/4 of the area of a circle and it is called a reflex angle