2002 Math OSK, Number 3: Raising Rules

What is the largest positive integer n n such that 8 n 8^n divides 4 4 44 44^{44} ?

88 22 29 8 44

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2 solutions

Eric Escober
Apr 4, 2015

Note first that

44 = 2 2 × 11 44 = 2^2 \times 11 .

Next, we evaluate

4 4 44 = 2 88 × 1 1 44 44^{44} = 2^{88} \times 11^{44}

4 4 44 = ( 2 3 ) 29 × 2 × 1 1 44 44^{44} = {(2^3)}^{29} \times 2 \times 11^{44}

4 4 44 = 8 29 × 2 × 1 1 44 44^{44} = {8}^{29} \times 2 \times 11^{44}

From this we see that 4 4 44 44^{44} is divisible by 8 29 8^{29} . Thus, n = 29 n = 29 .

Nice solution, but I think you meant ( 2 3 ) 29 (2^3)^{29} , because the parentheses make a hell of a difference. xD

Rick B - 6 years, 1 month ago

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yeah thanks for the clarification! cheers! :)

Eric Escober - 6 years, 1 month ago

Whoa .... very nice...upvoted :)

Vaibhav Prasad - 6 years, 2 months ago

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thank you :)

Eric Escober - 6 years, 2 months ago
Noel Lo
Apr 9, 2015

I'm the first to like this problem! Good one!!!!

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