What is the units digit in the standard decimal expansion of the number 7^25?(A)1(B)3(C)5(D)7(E)9

问题描述:

What is the units digit in the standard decimal expansion of the number 7^25?
(A)1(B)3(C)5(D)7(E)9

在标准十进制表示中7的25次方的个位数是多少
这个要找规律的
7^1 = 7
7^2 = 49
7^3 = 343
7^4 = 2401
7^5 = 16807
7^6 = 117649
7^8 = 823543
7^8 = 5764801
7,9,3,1个位数每4次一循环,25/4 余1因而是9