Numerical answer
Two chords AB and CD of a circle intersect at a point P inside the circle. If AP = 6 cm, PB = 8 cm and CP = 4 cm, what is the length of chord CD (in cm)?
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Answer: 16
By the intersecting-chords theorem, AP × PB = CP × PD.
6 × 8 = 4 × PD ⇒ PD = 12 cm.
CD = CP + PD = 4 + 12 = 16 cm.
Trap: Answering 12 (only PD) when the question asks for the whole chord.
6 × 8 = 4 × PD ⇒ PD = 12 cm.
CD = CP + PD = 4 + 12 = 16 cm.
Trap: Answering 12 (only PD) when the question asks for the whole chord.
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