Q: "What is the circumference and diameter of the Earth?"

Circumference: 80,150 km (49,802 miles) Diameter: 40,073 km (24,900 miles)

Before I begin, where do these numbers come from? I could not figure that out, so a source would be wonderful. Now the actual reason I started this topic is because these numbers don't make any sense. If the Earth does have a set diameter and circumference, that means it is not infinite, so it is a disk. Great. If we're only considering the top of the Earth, it is a circle, so you can calculate the circumference or diameter from the equation C = (pi) (d) where C is circumference, pi is 3.14, and d is the diameter. The problem is that the numbers given do not make any sense. If I plugged them in, this is what happens:

C = (pi) (d)

80,150 km = (3.14) (40,073 km)

80,150 km = 125,829.22 km

Now the problem is obvious, because the two sides do not match up. So now we have a few possibilities here

The first possibility is that the diameter is correct, and the circumference is wrong. If this is true, then the circumference should be 125,829.22 km

The second possibility is that the circumference is correct, and the diameter is wrong. If this is true, then the diameter should be 25,525.48 km

The third possibility is that both numbers are correct, but the earth is actually an ellipse. Now This means that the diameter must be one of the axis', so I worked it out, and I literally could not find a value for the short axis in order to validate this. Even if the short axis is infinitely small, the circumference has to be greater than 80,000 km (somewhere around 89,000 km) so an ellipse could not work at all.

So what's going on here? Is the circumference listed wrong, or is it the diameter? And is it really smart to trust a source that (a) has not been given, and (b) that has made such a simple mistake? Or did I just mess up somewhere along the way?