One friend claims that a dual-core system runs at twice the speed as a single-core system; another friend disagrees by saying that it runs twice as many programs at the same time; a third friend says it runs twice as much data at the same time. Explain who is correct and why?

the first friend

Explanation:

It is important to remember that a core is the brain of the CPU (central processing unit), which means one who has a dual-core is having "a dual brain" to process information faster.

Consider also, IT experts often acknowledge that in terms of speed of execution, it is proven that, "dual-core systems" are faster (even twice faster) than a "single-core system". The other friends were wrong because they disagreed with a widely accepted fact that dual-core is faster than single-core; and of course, we know that without them being faster they can't run twice the applications and twice the data.

Therefore, we can make the conclusion that the first friend's response is correct.