The object of this quiz is to adjust each circle's radius so it contains the target population shown at the right but ONLY within Europe. When you click Start you will be shown a marker on a random populated Europe grid square (there are over 90K 10x10 km grid squares used for the data, courtesy of https://human-settlement.emergency.copernicus.eu/index.php). Also you will see an adjustable circle of radius 100 km to start. Adjust the circle's radius by dragging it until it contains the target number of people shown - this target will be between 5 and 100 million people. Then click submit. You are scored on how close your circle's population is to the target.
PLEASE NOTE: ALL of Turkey is included in counting population (not just European portion), and the portion of Russia west of 61.5 degrees E (just east of Chelyabinsk). Nothing outside Europe (such as Africa or middle east other than Turkey) is included toward the population count within a circle.
Quiz Takers 
Where is Dublin – Belfast? The distance is like 150 km.
need to begin with same letter 🙂
The distances are a bit strange and inconsistent.
For #2 both cities directly border each other, so the distance must be between city centers. Which seems to work with the 21.4 km given.
For #3 the closest edges of the city limits are about 34km apart, and quite a bit further for the city centers.
yeah it’s like city centroids I think when measuring the distances, so may not be exactly where you might think the distance should exactly be.
For #20, please consider accepting the alternate (local) spelling that most of the quizzes accept.