How to prove you are smart enough to work at Google

HOW many houses in Canada are painted red?” That question recently greeted an applicant for an advertising position at Google. Crazy estimation questions have become popular in many industries, particularly as the job market has tightened. Job seekers are confronting posers like: How many surgeons are there in Britain? How many people are talking on their mobile phone right now? How many rubbish collectors are there in France?

Such questions are part of a general trend toward tougher, more invasive job interviews. Instead of merely asking a job candidate to say what he or she can do, interviewers are demanding that the candidate demonstrate skills in the interview. The rules are disarmingly simple: the interviewee is expected to use mental maths to come up with a specific figure – no paper, much less a computer, allowed.

Does it make sense for employers to ask these questions? They cite the job market: with so many qualified applicants for each open position, they need ways to winnow the field. Interviewers also complain that many applicants, even those with brilliant education or resumes, often have a problem applying what they know to the real world. While these estimation questions are sometimes intentionally bizarre, they parallel the sort of estimates common in the business world. The businessperson confronts a constant stream of opportunities: to open a new store or a new market; to develop a novel product or pull the plug on an underperforming line of business. It’s necessary to have a quick way of distinguishing the ideas worthy of further study from those that can be ruled out immediately. The smart entrepreneur has the knack of making quick offhand calculations of market size, costs, and profit.

Here’s how to handle “how many houses in Canada are painted red?” The first test is whether you have some demographic facts at your fingertips. The population of Canada is around 30m. If you don’t know that, at least be able to make a guess that isn’t totally ridiculous.

There are usually several people to a household. Let’s say three on average to keep it easy. Divide 30m by three to get 10m housing units. Not all of these are houses. Let’s say half are houses and half are apartments. That’s 5m houses.

How many are painted red? Not many. A door might be painted red, but it’s pretty unusual to have a whole house painted red. At a rough guess, only one in a hundred houses might be red. Divide 5m into 100 to get the answer: 50,000 red houses in Canada.

Any interviewer would be pleased with this answer. The interviewers who ask these kinds of questions don’t know the “correct” answer. They just want to see your thought process. Make sure it’s logical and grounded in a few real-world facts, and you’ll do fine.

Are You Smart Enough to Work at Google by William Poundstone is published by Oneworld, priced £12.99.