Manas1212
Consider a rectangle ABCD of area 90 units. The points P and Q trisect AB, and R bisects CD. The diagonal AC intersects the line segments PR and QR at M and N respectively. What is the area of the quadrilateral PQMN ?
A)> 9.5 and ≤ 10
B)> 10 and ≤ 10.5
C)> 10.5 and ≤ 11
D)> 11 and ≤ 11.5
E)> 11.5
In \(\triangle AMP\) and \(\triangle CMR\)
\(\angle MAP\) = \(\angle MCR\)
\(\angle AMP\) = \(\angle CMR\)
Therefore, we can say that \(\triangle AMP\) and \(\triangle CMR\) are similar
Hence, we can say that
\(\frac{AP}{CR}\)=\(\frac{MP}{MR}\)
⇒\(\frac{AB/3}{AB/2}\)=\(\frac{MP}{MR}\)
⇒ MR = \(\frac{3}{2}\) MP
⇒ MR = \(\frac{3}{4}\) RP ... (1)
Similarly, In \(\triangle ANQ\) and \(\triangle CNR\)
\(\angle NAQ\) = \(\angle NCR\)
\(\angle ANQ\) = \(\angle CNR\)
Therefore, we can say that \(\triangle ANQ\) and \(\triangle CNR\) are similar
Hence, we can say that
⇒\(\frac{2AB/3}{AB/2}\)=\(\frac{NQ}{NR}\)
⇒NR = \(\frac{3}{4}\) NQ
⇒NR = \(\frac{3}{7}\) RQ... (2)
In \(\triangle RMN\) and \(\triangle RPQ\)
\(\frac{Area of Triangle RMN}{Area of Triangle RPQ}\)=\(\frac{0.5 RM*RN*Sin MRN}{0.5 RP*RQ*Sin PRQ}\)
So Area of \(\triangle RMN\) = \(\frac{3}{5}\) * \(\frac{3}{7}\) * 15 = \(\frac{27}{7}\)
We know that, Area of triangle RPQ = 1/6*Area of rectangle ABCD = 1/6*90 = 15 sq. units
Hence, the area of the quadrilateral PQNM = 15 - \(\frac{27}{7}\) = \(\frac{78}{7}\) sq. units. Therefore, option D is the correct answer.
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