What is the units digit of (147^25)^50 ?  Choose the correct choice
A) 1 B) 3 C) 5 D) 7 E) 9

Rationale: the units digit of the exponents of 7 repeat in a cycle of four , which is { 7,9 , 3,1 } . the number 25 has the form 4 n + 1 so the units digit is 7 inside the bracket . the exponent 50 has the form 4 n + 2 , so the units digit is 9 . the answer is e .
Answer: E