Last Two Digits of Power

CAT 2008 Slot 1 · QA · Easy · Number System

What are the last two digits of 720087^{2008}?

  1. A.

    21

  2. B.

    61

  3. C.

    01

  4. D.

    41

  5. E.

    81

Answer

C

Explanation

The last two digits of 74n7^{4n} are always 0101.

For example: 74=2401017^4 = 2401 \rightarrow 01 78=5764801017^8 = 5764801 \rightarrow 01

Since 20082008 is divisible by 4, 720087^{2008} ends in 0101.

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