Any time you have to do a unit conversion, you will be either multiplying or dividing. One way to talk yourself through a unit conversion like this is to tell yourself "if it can do 6000 revolutions per minute, it must be able to do fewer revolutions in a second." That means you have to divide by 60, since there are 60 seconds in a minute. So since 6000/60 = 100, it can do 100 revolutions in one second. If it has x seconds, it must be able to do 100x revolutions in x seconds, so the answer is B.
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