# does anyone know the answer to this??

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#### sinfin

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I had a research interview the other day and I was asked, "if you are standing on a bridge that went over a river, how would you measure the amount of water that flowed under the bridge?"
There is no budget for the materials you could use to solve the problem.

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Where does the river end up? Begin?

I don't think there is a "right" answer. I think hey want to see your problem solving capabilities and how you approach a novel problem. I'd take some kind of depth measurements at 1/4 in, the middle, 1/4 to the other shore. Then I'd use some geometry to figure out how much a centimeter thick"wall of water" in the river would be. Toss something in the middle of the water that floats and count to ten or some other number. Then figure out the distance travled per second by the object, do the division. xxxx ccs/sec.

measure the area of the river and multiply it by the flow velocity. then multiply by time elapsed.