16Hit1600
Geometry and TrigonometryEasy–MediumDiagonal brace of a rectangular lid

Geometry and Trigonometry practice question

A rectangular lid measures 5 decimetres by 12 decimetres. A straight brace runs from one corner of the lid to the opposite corner. How long, in decimetres, is the brace?

Answer: 13

The brace is the diagonal — the hypotenuse of a right triangle with legs 5 and 12: √(25 + 144) = √169 = 13.

Common wrong answers

If you answered 17
17 is 5 + 12, the two sides added; the diagonal is shorter than that.
If you answered 60
60 is 5 × 12, the lid's area, not a length.
If you answered 169
169 is 5² + 12²; take the square root.

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