Christian, that question would work but better in knots. Better yet at 420 kts and 180 or 240 knots. Play around with those numbers and see if you can figure why. There is probably references to these in this thread.
As for web tests, you don't need that, just make up your questions, work them out mentally then check your answers in slower time.
For example, you are in your car, you are doing 54 mph, you have 9 miles to go - how long to get there, what time will you get there, what fuel will you need assuming 30 mpg. Your journey is 210 miles. What is your eta? How much fuel? Hint - you buy fuel in litres.
Then consider that eta and recalculate the speed required for a different eta.
Real world, on the hoof, SDT will beat CBT every time.
As an aside, a good few years ago there was an advert for the RAF. You had to establish the time to intercept an inbound bomber. You had to consider speeds, fuel, distances to target, intercept and tanker. It was a superb intellectual exercise and pilots and navigators came up with different answers, all accurate but some better than others.