What is the units digit of ?
Answer and explanation
Correct answer: C.
- Step 1: The units digits of powers of repeat in a -term cycle (). Because , the remainder is , so ends in .
- Step 2: The units digits of powers of also follow a -term cycle (). With remainder , ends in .
- Step 3: Add the units digits: , giving a units digit of .
Answer
.
Why not the others: is the units digit of alone; is an arithmetic addition error (); is the units digit of alone; is the units digit of or .
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