In the figure above, if the length of MO is 10

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In the figure above, if the length of MO is 10

by M7MBA » Fri Apr 05, 2019 11:37 am

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In the figure above, if the length of MO is 10, is MNO an equilateral triangle?

(1) The length of MN is 10.
(2) h = 5√3

[spoiler]OA=E[/spoiler]

Source: Princeton Review

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by Ian Stewart » Fri Apr 05, 2019 3:54 pm

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If you knew that the seemingly-vertical line of length 'h' was at right angles to the line MO, then it would be easy, with both statements, to use Pythagoras to find the lengths of all of the sides. But without knowing if we have a right angle there, we can't do much, and the answer is E.

They're trying really hard to be 'tricky' here, not only by drawing the 'vertical' line so it appears to be perpendicular to the horizontal line MO, but also by labeling it with the letter 'h' to make it seem to be a height of the triangle. I suppose it's a good warning to be careful about the assumptions you make.
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