None of these seem particularly difficult, as long as the person answering isn't trying to blurt out the first number that pops in their head as fast as possible.

Their conclusion after the first question:

> those who answered 10 cents were found to be “significantly less patient” than those who answered correctly.

Patients really seems like the main thing being tested here. 2 and 3 are also pretty common brain teaser questions, so it can simply be a matter of exposure to them.