有什麼方法計到?????????

2010-01-28 2:13 am
有1只小猴子,他剛學會爬樹,每爬3米就下跌1米,每爬1米要1秒,每下跌1米也要1秒,他現在要爬30米的樹,他要多少秒才爬完?

        28除2乘4加2
=58秒

Q1.我想問問,28是怎得出來的??? 28是怎得出來的???

Q2.我想問問有什麼方法計到28?(一定要快捷的方法!)
(一定要快捷的方法!)

回答 (2)

2010-01-31 6:23 am
✔ 最佳答案
其實要解呢條問題唔系要知28點來,系要知呢條問題是供的資料作分析:
每爬3米就下跌1米,每爬1米要1秒,每下跌1米也要1秒
即是爬1米或2米唔會下跌,只有最接近30米時先可以只爬1米或2米,咁即系28米或29米時唔會下跌
即系頭28米或29米時,每爬2米要4秒,由於每次系爬2米,所以冇可能會下跌到29米,所以一定系28米時再用2秒爬上30米
所以系[(28/2)X4]+2
2010-01-29 12:58 am
Q1.For 2 seconds,
Distance = 1x2 = 2m
Speed = 2/2 = 1m/s

For 4 seconds,
Distance = 1x3 - 1 = 2m
Speed = 2/4 = 0.5m/s

For 28 meters,
Time = 28/0.5 = 56s

56/4 = 14
the monkey drops at t = 56s

For the last 2 meters,
Time = 2/1 = 2s

Total time cost = 2 + 56 = 58s

28 is the first 28m and the last drop of the monkey is ended.

Q2.Some may think the time needed is 30/0.5 = 60s, but the monkey arrives 30m, it is no need to count its drop after 2s.


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