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The least non-negative remainder when 21012^{101} is divided by 5 is:

Solution

✅ Correct Option: 3

To find the remainder when 21012^{101} is divided by 5, calculate the first few powers of 2 and their remainders when divided by 5:

PowerValueRemainder when ÷ 5
212^122
222^244
232^383
242^4161
252^5322
262^6644

The remainders repeat in the pattern: 2, 4, 3, 1, 2, 4, 3, 1...

The pattern repeats every 4 powers.


Since the pattern repeats every 4 powers, divide 101 by 4:

101=4×25+1101 = 4 \times 25 + 1

The remainder is 1, which means 21012^{101} has the same remainder as 212^1 when divided by 5.


From the pattern above, 212^1 gives remainder 2 when divided by 5.

Therefore, 21012^{101} gives remainder 2 when divided by 5.

The answer is 2.

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