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Answers
TO PROVE : AR = 3/7AC
PROOF : Since ABCD is a ||gm , then AB || CD and AD || BC.
Since AB || CD and AC is a transversal, so
∠PAR = ∠QCR (Alternate interior angles) .........(1)
Since ABCD is a ||gm , then AB = CD and AD = BC , as opposite sides of ||gm are equal.
Let AB = CD = x
so, AP = 3x/5 and PB = 2x/5 [as, AP:PB = 3:2]and CQ = 4x/5 and QD = x/5 [as, CQ:QD = 4:1]
In △CQR and △APR, ∠QCR = ∠PAR [using (1)]∠QRC = ∠PRA [vertically opposite angles]⇒△CQR ~ △APR [AA similarity]
⇒CR/AR = CQ/AP=QR/PR (corresponding sides of similar △'s are proportional)⇒CR/AR = CQ/AP⇒CR/AR =4x/5=3x/5⇒CR/AR =4/3⇒CR/AR + 1= 4/3 + 1⇒CR + AR/AR = 7/3⇒AC/AR = 7/3⇒7AR = 3AC⇒AR = 3/7AC
Answer:GIVEN : ABCD is a ||gm , in which P is a point on AB such that AP : PB = 3 : 2 and Q on CD such that CQ : QD = 4 : 1.
TO PROVE : AR = 3/7AC
PROOF : Since ABCD is a ||gm , then AB || CD and AD || BC.
Since AB || CD and AC is a transversal, so
∠PAR = ∠QCR (Alternate interior angles) .........(1)
Since ABCD is a ||gm , then AB = CD and AD = BC , as opposite sides of ||gm are equal.
Let AB = CD = x
so, AP = 3x/5 and PB = 2x/5 [as, AP:PB = 3:2]and CQ = 4x/5 and QD = x/5 [as, CQ:QD = 4:1]
In △CQR and △APR, ∠QCR = ∠PAR [using (1)]∠QRC = ∠PRA [vertically opposite angles]⇒△CQR ~ △APR [AA similarity]
⇒CR/AR = CQ/AP=QR/PR (corresponding sides of similar △'s are proportional)⇒CR/AR = CQ/AP⇒CR/AR =4x/5=3x/5⇒CR/AR =4/3⇒CR/AR + 1= 4/3 + 1⇒CR + AR/AR = 7/3⇒AC/AR = 7/3⇒7AR = 3AC⇒AR = 3/7AC