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Bunuel
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Poju4real
Prime factorization of 405 is
3^4×5.
Therefore, (405)^4 = (3^4×5)^4
= 3^16×5^4. Since 3^16×5^4 is a multiple of 3^x, in other words, 3^x is a factor of 3^16×5^4. 3^x = 3^16, x = 16.
The largest possible value of x is 16.

Option C.

Posted from my mobile device

I have exactly the same, why is it wrong though? :shh:
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Bunuel
If X is a positive integer and 405^4 is a multiple of 3^X, what is the largest possible value of X?

(A) 5.
(B) 12.
(C) 16.
(D) 20.
(E) 26

Given: \(405^4=3^xk\).

\(405^4=(3^4*5)^4=3^{16}5^4=3^xk\). Hence the largest possible value of x is 16 (for \(k=5^4\))

Answer: C.
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Bunuel
If X is a positive integer and 405^4 is a multiple of 3^X, what is the largest possible value of X?

(A) 5.
(B) 12.
(C) 16.
(D) 20.
(E) 26

Given: \(405^4=3^xk\).

\(405^4=(3^4*5)^4=3^{16}5^4=3^xk\). Hence the largest possible value of x is 16 (for \(k=5^4\))

Answer: B.

What now?

"The largest possible value x is 16, Answer B"

B is 12 though, what is the right solution now? :dazed
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How B ?

Max value of X is 16

Posted from my mobile device
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Richa2816
How B ?

Max value of X is 16

Posted from my mobile device
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The OA is C, 16.
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