The longest side of an obtuse triangle measures 20 cm. the two shorter sides measure x cm and 3x cm.

rounded to the nearest tenth, what is the greatest possible value of x?

6.3
6.4
7.0
7.1

If an obtuse triangle is given and 20 cm is the longest side, then: 

x² + (3x)² < 20²
x² + 9x² < 400
10x² < 400
x² < 40
x < 6.3

So, the greatest possible value of x could be 6.29999... ≈ 6.3 to the nearest tenth.

The answer would be 484

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