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In the adjoining figure, ABCD is a parallelogram. If P and Q are mid-points of sides CD and BC respectively. Show that CR = 14\dfrac{1}{4}AC.

In the figure, ABCD is a parallelogram. If P and Q are mid-points of sides CD and BC. Show that CR = (1/4)AC. Mid-point Theorem, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mid-point Theorem

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Answer

In parallelogram, diagonals bisect each other.

∴ AO = OC = 12\dfrac{1}{2}AC ……(i)

In △BCD,

P and Q are midpoints of CD and BC,

PQ || BD (By midpoint theorem)

Since, PQ || BD

∴ QR || BO

In △BCO,

Q is midpoint of BC and QR || BO

∴ R is midpoint of OC

CR = 12\dfrac{1}{2}OC

Substituting value of OC from (i) in above equation,

CR = 12\dfrac{1}{2}OC = 12×12×\dfrac{1}{2} \times \dfrac{1}{2} \times AC = 14\dfrac{1}{4}AC.

Hence, proved that CR = 14\dfrac{1}{4}AC.

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