How about these for terrible interview
"How many Smarties can you fit into a coffee cup?"
"How many windows does this building have?"
"How many planes are flying above London right now?"
"How many times heavier is an elephant than a mouse?"
They sound like the makings of a bad Maths exam, but law firm interviewers can occasionally ask questions like this. They're an excellent test of your ability to think on your feet and keep calm and articulate under pressure.
Here's how to answer:
1. Don't rush - think carefully through the problem, ideally with a paper and pen.
2. Make some assumptions using simple numbers - how big is the coffee cup/building/window? How heavy is an elephant? How heavy is a mouse? You're not expected to know, just to have a realistic estimate. Use round numbers/weights - you don't want to get bogged down in calculations.
3. Explain your thought process and assumptions to the interviewer: "This is a square five storey building with windows on all sides. Let's assume that the building has a height of twenty metres and that each window is two metres high and one metre wide..."
Nobody's really expecting you to know the right answer. However, they are expecting you to take the question seriously and answer it methodically - just as you'd be expected to do in practice.