A K-number is a positive integer with the special property that 3 times its unit

游客2024-01-12  9

问题 A K-number is a positive integer with the special property that 3 times its units’ digit is equal to 2 times its tens’ digit.

Column A                                             Column B
The number of K-numbers between 10 and 99            3

选项 A、if the quantity in Column A is greater
B、if the quantity in Column B is greater
C、if the two quantity are equal
D、if the relationship cannot be determined from the information given

答案 C

解析 K是一个具有特殊性质的正整数:其个位数(units)的3倍等于十位数(tens)的2倍。
解:本题的正确答案为(C)。该题中的K-number为题中定义的一个函数,其个位数与十位数的关系为:3m=2n(m为个位数,n为十位数)。题目中的左项为10到99之间的K整数的数目,而满足方程3m=2n的数只有m=2,4,6;n=3,6,9。也就是10至99之间的K整数有32,64,96。
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