The three questions you need to answer to get a job at a billion-dollar startup

Billion-dollar tech startups are so rare they are known as unicorns.

Office software firm Slack is one of them and in an interview with the New York Times, its CEO and co-founder Stewart Butterfield has revealed how he chooses prospective workers.

Rather than the notoriously complex inquiries favoured by some tech companies, Butterfield said he used to ask prospective employees three basic questions, one about maths, one about geography and one about history. They were:

1. What is 3 x 17?

2. Name three countries in Africa

3. What century was the French Revolution in?

His rationale? "I didn’t expect people to get the answers right, but I just want them to be curious about the world."

Butterfield now asks candidates what they want to be when they grow up, with a good answer focusing on areas people want to grow in or things people want to learn and a bad one being anything "very short".

But for those in their 20s who still don't have an answer at all, the 42-year-old entrepreneur has some good news:

I certainly didn’t have anything figured out by the time I was 25... I still don’t have certain things figured out.

(Note: the answer to question one is 51 and to question three is the 18th century or 1787-1799)

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