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# If 7^9 + 7 9 + 7^9

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If 7^9 + 7 9 + 7^9 [#permalink]  18 Jul 2018, 16:51
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Question Stats:

53% (00:16) correct 46% (00:57) wrong based on 13 sessions
If $$7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 = 7^x$$ , what is the value of x?

(A) 9
(B) 10
(C) 12
(D) 63
(E) $$9^7$$

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[Reveal] Spoiler: OA

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Re: If 7^9 + 7 9 + 7^9 [#permalink]  18 Jul 2018, 19:57
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Carcass wrote:
If $$7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 = 7^x$$ , what is the value of x?

(A) 9
(B) 10
(C) 12
(D) 63
(E) $$9^7$$

Kudos for R.A.E.

Given,
$$7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 = 7^x$$

or $$7^9 ( 1 + 1 + 1 + 1 + 1 + 1 + 1 ) = 7^x$$

or $$7^9 (7^1) = 7^x$$

or $$7^{10} = 7^x$$

or $$x = 10$$
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Re: If 7^9 + 7 9 + 7^9 [#permalink]  19 Jul 2018, 12:07
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Carcass wrote:
If $$7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 = 7^x$$ , what is the value of x?

(A) 9
(B) 10
(C) 12
(D) 63
(E) $$9^7$$

Kudos for R.A.E.

Given

$$7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 + 7^9 = 7^x$$

= $$7^9$$ ( 1 + 1 + 1 + 1 + 1 + 1 + 1 )

= $$7^9$$ * $$7^1$$

= $$7^{10}$$

So x must be 10.

The best answer is B.
Re: If 7^9 + 7 9 + 7^9   [#permalink] 19 Jul 2018, 12:07
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# If 7^9 + 7 9 + 7^9

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