问问题描述
答精选答案

1至9能组成的三位数太多了:123,132,213,231,312,321,124,142,214,241,412,421,134,143,314,341,413,431,125,152,251,215,512,521,126,162,216,261,612,621,127,172,217,271,712,721,128,182,218,281,821,812,129,192,219,291,912,921,358,385,974,947,986,968,978,827,872,956,865………
答其他回答(3条)
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数字1至9一共可以一共可以组成729种三位数。
1、每个位都是独立的,那么就可以组成9*9*9=729个数字
2、三位数共100~999,共900个数,其中每个x00~x99的含0个数相同
x00~x09 共10个0 剩余x10
x20
..
x90共9个
所以900-(10+9)*9=729个
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这一道题目,我们一致就能指上哪个哪些三位数,也不是要问我们遇到酒里面组成的三位数有多少?
首先我们知道1~9里面总共有九个数字,组成三位数的话,我们用9×3,9×3也就等于27,所以一致就能住上27个三位数。做这种题目的话,我们就需要仔细去学我们的乘法定理就可以了。
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112.113114.115.116.117.118.119.121.131.141.151.161.171.181.191.211.221.223.224.225.226.227.228.229.311.322.344.355.366.377.388.399.411.422.433.455.466.477.488.499.511.522.533.544.556.557.558.559.661.662.663.664.665.667..668.669.771.711.722.733.744.755.776.778.795.799.等等1到9组成的三位数字有这些。
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本文概览:1至9能组成的三位数太多了:123,132,213,231,312,321,124,142,214,241,412,421,134,143,314,341,413,431,125,152,251,215,512,521,126,162,216,261,612,621,127,172,217,271,712,721,128,182,218,281,821,812,129,192,219,291,912,921,358,385,974,947,986,968,978,827,872,956,865………