An earthworm starts moving towards a point 1.8cm away at a pace of 1cm per minute. As it gets tired, it covers only half the distance compared to previous minute in each succeeding minute. How long will it take to reach its target?
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2008-09-24 5:04 am
回答 (1)
2008-09-24 6:30 am
✔ 最佳答案
1.8cm = 1cm + 0.5cm +0.25cm + 0.125cm + ... + (0.5 ^ n)= {1 - [0.5 ^ (n + 1)]} / (1 - 0.5)
= {1 - [0.5 ^ (n + 1)]} / 0.5
so,
0.1 = [0.5 ^ (n + 1)]
ln (0.1) = ln [0.5 ^ (n + 1)]
n = ln (0.1) / ln (0.5) - 1 = 2.322
收錄日期: 2021-04-23 18:10:00
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080923000051KK02078