If \(z\) is an odd integer, is \(300z > 1500?\)

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Source: — Data Sufficiency |

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by Vincen » Sun Jun 30, 2019 10:19 am

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Gmat_mission wrote:If \(z\) is an odd integer, is \(300z > 1500?\)

\((1 )\ 0 < \sqrt{z} < 8 \)
\((2) \ 1 < z^2 < 45\)

[spoiler]OA=B[/spoiler]

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Hi Gmat_mission. This is how I would solve this DS question.

Statement 1:
\((1 )\ 0 < \sqrt{z} < 8 \)

Since \(0 < \sqrt{z} < 8 \) then we have that \(0 < z < 64 \). Now:
- If z=1 then \(300z < 1500,\) and so the answer is NO.
- If z=63 then \(300z > 1500,\) and so the answer is YES.
We've got two different answers, then this statement is Not Sufficient.

Statement 1:
\((2) \ 1 < z^2 < 45\)

Since \(z\) is an odd integer and \(1 < z^2 < 45\) then \(1 < z < 7\) which implies that \(z=3\) or \(z=5\). Here, in any case, we will get that \(300z \leq 1500,\) and so, the answer is NO.
Here, we've got a unique answer. Therefore, this statement is Sufficient.

In conclusion, the correct answer is _B_.

I hope it helps you. <i class="em em-sunglasses"></i>

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by Ian Stewart » Mon Jul 01, 2019 5:43 am

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Vincen wrote: Since \(z\) is an odd integer and \(1 < z^2 < 45\) then \(1 < z < 7\) which implies that \(z=3\) or \(z=5\).
It's also possible that z is negative, so z can also be equal to -3 or -5. That doesn't change the answer to the question though.

I'd find it useful to rephrase the question by dividing by 300 on both sides: we want to know "is z > 5?"
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