The product of two consecutive positive integers CANNOT beA、a prime numberB、div

游客2024-01-12  15

问题 The product of two consecutive positive integers CANNOT be

选项 A、a prime number
B、divisible by 17
C、a multiple of 13
D、an even number less than 10
E、a number having 4 as its units digit

答案 E

解析 此题可采用排除法。A有反例:1×2=2为质数;B有反例:17×18可以被17整除;C有反例:13×14是13的倍数;D有反例:2×3=6<10;因此选E。再来看看E为什么不对:因为4=1×4=2×2,若乘积个位数为4,则需由个位数为1和个位数为4的两个数,或者个位数均为2的两个数相乘,不可能是两个连续整数的乘积。
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