A bacterium is so prolific that it doubles in size every day. How many days will it take to multiply to 16,000 if the first day breeds 2,000 and the second day 4,000?
一种细菌的繁殖能力很强，每天增长一倍．第一天繁殖到2000个，第二天繁殖到4000个，那么繁殖到16000个需多少天．
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