请教各位下面题的解题思路
we had to design a colour code for all the books in our class library. we decided to have 5 stripes on each book, we could colour each stripe in one of the three colours. it didn't matter if more than one stripe have the same colour, not even if they were adjacent. but we could not have all the stripes the same colour. how many different books could we code in this way?
like this
多谢啦
评论
the answer is 160 !
评论
160
评论
why?
评论
the correct answer is 240. but i don't know how it is worked out.
评论
这是精英考试题，选自Mathematics 100 mini Exams, marked as "容易" ..
请高人指点
评论
这是一道运用“乘法法则”的题目。
如果随便怎么涂色的话，有 3 x 3 x 3 x 3 x 3 = 243 种涂色方法。
但是，其中全部5个stripe全部颜色一样的有3种。
所以，243 - 3 = 240 种。
评论
我也算的是240
评论
3^5-3=240
澳洲中文论坛热点
- 悉尼部份城铁将封闭一年，华人区受影响！只能乘巴士（组图）
- 据《逐日电讯报》报导，从明年年中开始，因为从Bankstown和Sydenham的城铁将因Metro South West革新名目而
- 联邦政客们具有多少房产？
- 据本月早些时分报导，绿党副首领、参议员Mehreen Faruqi已获准在Port Macquarie联系其房产并建造三栋投资联