It's not even that simple, because back in the single core days, AMD was taking Intel to task with their Athlon line compared to the Pentium 4, because for every clock cycle AMD's CPU processed more data, so for many tasks it was actually faster even at a lower clock speed. Which is why Intel kind of went back to the drawing board with the Core line.
But the point of multi-core systems isn't really so much speed as fluidity. Even if one core is busy performing some complicated task, you have another core that's free to handle the routine tasks that make an operating system work, and so you don't notice any reduced responsiveness to the system as a whole. That's the ideal scenario, multi-core setups take a few shortcuts to reduce price from multi-CPU setups, but it is still better than a single core.
So while maybe not a perfect analogy, it should get the basic point across. Think of your CPU like a freeway. The clock speed would be the speed limit, and then the number of cores would be how many lanes of traffic there are. So, say you have 100 cars that need to get from Point A to Point B. With a single core CPU, it'd be like a one lane highway, every car has to travel single file, and so the idea was just to increase the speed limit as much as possible to get each individual car through as quickly as possible. You could liken AMD's more work per clock cycle to making sure that the road is nice and smooth, no potholes or anything else that may slow cars down regardless of the speed limit. Anyway, now if you have 2, 4, 6, even 8 lanes of traffic, all with the same speed limit... In an ideal scenario you can have that many cars moving between Point A and B at a time. They are all moving at the same speed, you just have more of them going at a time.
It's not quite that simple, because multi-core CPUs are such that every core shares the same set of data pathways in and out, so only one core can either send data out or get new data to process. So, despite the best efforts of the CPU engineers who will work very hard to try and make sure the CPU schedules tasks internally to try and avoid this, at some point one or more cores is going to have to sit and wait for another core to finish sending/receiving data before it can send/receive data. So I suppose you can think of it like those really short merge areas anyone who's lived in a big city has undoubtedly seen, where two freeways come together and traffic tends to back up because you might have 2-4 lanes that all converge into one within maybe a quarter mile, and people have to sort themselves out to avoid an accident.
Also, just to correct Mark quickly, each core is running at 3.2GHz. You don't divide the rated speed by the number of cores.
In the early days where we had only one core per CPU it was easy to get an idea of the speed. For example a 3.0GHz has exactly that speed.
But these CPUs with cores baffle me. I now have an Intel Core i5-2410M @ 2.30GHz (4 CPUs). What's the speed of my CPU compared to a single core one?
Thanks in advance.

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