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If integer x is greater than 0 but less than 10 and k = x^9, what is t

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If integer x is greater than 0 but less than 10 and k = x^9, what is t [#permalink]

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If integer x is greater than 0 but less than 10 and \(k = x^9\), what is the value of integer k?

(1) x^2 has a units digit of 1.

(2) \(x^{(–2)} < \frac{1}{50}\)
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If integer x is greater than 0 but less than 10 and k = x^9, what is t [#permalink]

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New post 22 Aug 2017, 04:01
Bunuel wrote:
If integer x is greater than 0 but less than 10 and \(k = x^9\), what is the value of integer k?

(1) x^2 has a units digit of 1.

(2) \(x^{(–2)} < \frac{1}{50}\)


Answer has to be C because from statement 1 we get x = 1, 9 while from statement 2 x can be 8 or 9 .
Hence statement C is sufficient to ans the question because combining we get x to be 9.

Last edited by sandeep211986 on 22 Aug 2017, 04:05, edited 1 time in total.

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Re: If integer x is greater than 0 but less than 10 and k = x^9, what is t [#permalink]

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New post 22 Aug 2017, 04:02
Bunuel wrote:
If integer x is greater than 0 but less than 10 and \(k = x^9\), what is the value of integer k?

(1) x^2 has a units digit of 1.

(2) \(x^{(–2)} < \frac{1}{50}\)


Statement 1
- Since \(0<x<10\), we have 9 integer options for X.
- From that 9 options, we have two integers with 1 unit digit : \(1^2\) and \(9^2\).
- Therefore, INSUFFICIENT.

Statement 2
- \(\frac{1}{x^2} < \frac{1}{50}\).
- Since X is a positive number, we can cross multiply without change the sign.
- \(50 < x^2\), or \(X^2 > 50\). We have different possibilities here. X can be 8 and 9.
- Therefore, INSUFFICIENT.

Statement 1&2
- We can conclude that X must be 9.
- SUFFICIENT.
C
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Re: If integer x is greater than 0 but less than 10 and k = x^9, what is t [#permalink]

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New post 31 Aug 2017, 21:20
Another super careless mistake of mine,
I forgot 1, I only thought of 9^2= 8"1"

Kudos [?]: 3 [0], given: 454

Re: If integer x is greater than 0 but less than 10 and k = x^9, what is t   [#permalink] 31 Aug 2017, 21:20
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