Archit3110
Bunuel
Parallelogram PQRS has a perimeter of 24. PQ = 2QR and Angle PQR = 120 degrees. Parallelogram TQUV is formed by cutting out part of parallelogram PQRS so that angle TQU and PQR share the same angle. If TQUV is half the area of PRQS and TQ = 2QU, what is the perimeter of TQUV to nearest 0.1?
A. 15
B. 17
C. 18
D. 19
E. 20
chetan2u : I am not able to visualize this question on paper.. could you please look into the question..
See the figure attached...
let us take the first parallelogram. PQRS
PQ = 2QR
Perimeter - 2(PQ+QR)=2(2QR+QR)=6QR=24......QR=4 and PQ=2*4=8
Now let us see the area of PQRS
drop a perpendicular from Q on PS -> QA
Now PQA is 30-60-90 triangle as angle PQT = 120-90=30..
so if PQ is 8, height or PA will be \(8\sqrt{3}/2=4\sqrt{3}\)
Thus area = PS*QA = \(4*4\sqrt{3}\)=\(16\sqrt{3}\)...
so area of parallelogram TQUV is \(16\sqrt{3}/2=8\sqrt{3}\)..
now let QU be a, so TQ=2a...
height of TQUV will be TQ*\(\sqrt{3}/2=a\sqrt{3}\), as TQA' is also 30-60-90.
thus its area = \(a*a\sqrt{3}=a^2\sqrt{3}=8\sqrt{3}\), so \(a=2\sqrt{2}\)..
thus perimeter is 2(a+2a)=6a=6*\(2\sqrt{2}=12*1.414=17\)
B
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