In this lesson, you’ll learn what concentric circles are, and you’ll see a few examples of sets of concentric circles. Then, you can test your knowledge with a brief quiz.

## Playing Darts

Many of us are familiar with a dartboard:

But we don’t often think about a dartboard as several circles in one, forming the different rings. All of these circles happen to be drawn around a common center, the bullseye.

## Concentric Circles

A dartboard is really a set of **concentric circles**, which are circles that share a common midpoint. When circles are concentric, smaller circles will lie inside larger circles, regardless of how many circles are in the set.However, just because one circle is inside the other doesn’t necessarily mean they’re concentric circles. Take these circles, for example:

## Real-World Concentric Circles

The common image of a ship’s wheel includes two concentric circles joined by spokes:

Similarly, the grooves on this manhole cover form concentric circles, all centered around the manhole’s midpoint.

## Lesson Summary

**Concentric circles** are circles that share a common midpoint. An easy way to think of them is the circles on a dartboard that are all centered around the bullseye.

If circles have different midpoints, they’re not concentric.

## Lesson at a Glance

Concentric circles share a common midpoint. These circles usually lie inside each other, with the center typically being the midpoint. Just because one circle is inside the other doesn’t necessarily mean they’re concentric circles.

## Learning Outcome

Upon completing this lesson, you should be able to identify concentric circles.