There is no answers if you don't specify tons of parameters, like the number of element, prior memory fragmentation, etc.
200x can be a reasonable outcome. So can be 3x in other conditions.
As a rule of thumb I now consider that a completely random memory access is on the order of accessing 1000 sequential bytes.
My A+ answer is "My guess is [x] but instead of speculating we can create a test to discover the performance. [Describes test]."
Koala_man above says:
> I wrote a benchmark and found the difference in this case to be 3x-3.5x.
The actual number depends on a lot of things, of course (language, architecture, test methodology...), but it is possible that your 20-200x A+ answer is incorrect.