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Re: If 7^9 + 7 9 + 7^9 [#permalink]
Why cant i go with 7 to the power of (9x7) which would be 7 to the power of 63. And x = 63. Because the base is same which is 7.
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Re: If 7^9 + 7 9 + 7^9 [#permalink]
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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) \(9^7\)

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Key property: k + k + k + k + k + k + k = 7k
Similarly, 7⁹ + 7⁹ + 7⁹ + 7⁹ + 7⁹ + 7⁹ + 7⁹ = 7(7⁹) = ()(7⁹) = 7¹⁰

Answer: B
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Re: If 7^9 + 7 9 + 7^9 [#permalink]
Hey @Brent Hanneson, Yes! I realized it only after posting. Thank you for reverting back : )
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Re: If 7^9 + 7 9 + 7^9 [#permalink]
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I'm going to second GreenlightTestPrep 's approach here:

I just look at these as the same number added a bunch of times. If x + x + x = 3x, then we could say that 3 + 3 + 3 = 3^1(3) = 3^(1+1) = 3^2.

In the case that we have, it's 7^9 seven times: 7*7^9 = 7^(1+9) = 7^10. Answer B.
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Re: If 7^9 + 7 9 + 7^9 [#permalink]
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