Do the drawn circles have the same radii or the same center?
Concentric
Practice makes perfect
Let's begin by recalling that concentric circles are coplanar circles that have the same center. Congruent circles, however, have congruent radii. Looking at the given picture, we can see that circular plastic containers are placed one inside the other and have different sizes.
This means that they are not congruent — as they have different radii — but they are concentric, as they seem to have the same center.
Extra
Congruent and Concentric Circles
Let's review what we know about concentric and congruent circles. We will begin with the concentric circles.
Concentric Circles
Coplanar circles and have the same center.
Notice that the only thing that differs two concentric circles from each other are their radii. This means that they can be of different sizes as long as their center is the same. Let's take a look at an example.
Circles A and B are concentric circles, they have the same center, O. The area between two concentric circles is called annulus.
Next, let's recall the definition of congruent circles.
Congruent Circles
Circles that have congruent radii.
Let's take a look at an example.
Circles A and B are congruent, they have the same radii.
