An architect must lay out a parallelogram-shaped hall ABCD with AB=9 m, BC=7 m and the longer diagonal AC=14 m. Using the parallelogram law, the diagonals satisfy AC2+BD2=2(AB2+BC2). Find the shorter diagonal BD (in metres).
Class 8Constructing QuadrilateralsGeometry
A6
B8
C4
D10
Step-by-Step Solution
Parallelogram law: AC2+BD2=2(AB2+BC2)=2(81+49)=260. So BD2=260−142=260−196=64, giving BD=8 m.
Answer: B) 8
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