How would you calculate the speed at which the earth revolves around the sun in m/s?

Calculate from the average distance of earth from the sun and the time it takes to complete one orbit at about 3×10⁴ms−1

The average distance of the Earth from the Sun is approximately 150 million km or 1.5×10¹¹m

The orbit of the Earth around the sun can be taken as 365 days roughly

So the path that the Earth traverses in 365 days is approximately the circumference of a circle of radius 1.5×10¹¹m.

C=2πr to find that this is about 9.4×10¹¹m.

The number of seconds in 365 days is:

365 x 24 x 60 x 60=31536000

Thetangential velocity of the Earth is approximately:

9.4×10¹¹/3.1536×107≈3×10⁴ms−1

That is 30 km per second.