The tricky math question one CEO asks to size up job candidates

To add some pressure to an already intimidating situation, some employers require job candidates to meet with the company's CEO during the interview process.

That may sound a bit scary - but it's nothing compared to the questions some of these leaders actually ask.

Jeff Zwelling, cofounder of Convertro and CEO of ZipRecruiter, a job search engine, told Business Insider he often turns to unique, and sometimes tricky, questions during job interviews so that he can get a better sense of who the candidate is.

For example, in the middle of the conversation, he often throws in this curveball math question: A hammer and a nail cost $1.10, and the hammer costs one dollar more than the nail. How much does the nail cost?

It's simple, but tricky.

"Some candidates will instantly blurt out 10 cents, which is obviously wrong," he said. "They don't have to get the exact right answer, which is a nickel, but I want to see them at least have a thought process behind it."

Zwelling understands that math isn't everyone's forte, but he wants them to realize that "10 cents is too easy of an answer, and that if it was that easy, I wouldn't be asking it."

He also asks tricky questions, he said, to see how the candidate may perform on the job.

"If the person is hired, he or she will eventually have to sit across the table from top CMOs and will need to be able to answer the tough questions that come at them, to think on their feet, and to feel confident in their responses," Zwelling said.