These techniques work when they're relevant to the problem, but it's safer to use a common-sense method than to show off. This is the interview where the consultant wants you to estimate the number of golf balls in the U.S. and then multiply 752 x 13 in your head. These questions are common in first interviews when consultants want to weed out candidates who aren't budding Mensa members. They're also used to test applicants whose degrees aren't in science, economics or engineering. Refuse to be flustered.
Most problems are easier than they seem.
To solve them, you must make assumptions and sensible guesses. In the above example, estimate what proportion of the U.S. population plays golf and how many balls average golfers have in their club bags. As with case studies, how you think is more important than producing right answers. We're so impressed' A seemingly easy interview is often a deadly trap. Your interviewer puts you at ease, telling you how impressive your reasoning skills were in the previous round.