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PUNE MCA Exam 2015 Question Paper with answers for online practice

Question : 13 of 59

Marks: +1, -0

(13)^27

;

Solution:

Concept:

The unit digit of

13^{27}

is the same as the unit digit of

3^{27}

, since

13 \equiv 3 \pmod{10}

Explanation:

The pattern of unit digits for powers of 3 repeats every 4:

3^1 \to 3

3^2 \to 9

3^3 \to 7

3^4 \to 1

Divide the exponent 27 by 4:

27 \div 4

gives remainder 3.

Thus the unit digit corresponds to

3^3

, which is 7.

Answer:

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