ParadigmSpecialising in O Level Mathernatics5 In the diagram, ABC is a triangle where M is the midpoint of AC.The point P lies on the line BM such that BP=31BM.The point Q lies on the line BC such that BQ:QC=1:4.Given that AB=b and M0.(a) Express, as simply as possible, in terms of M1 and/or M2,(i) M3,(ii) M4,(iii) M5,(iv) M6.(b) Write down two facts about M7 and Q.(c) Find the numeral value of M9,Ans:(a)(i) AC0(ii) AC1(iii) AC2(iv) AC3(b) M7 and Q are collinear AC6(c) AC7
Q. ParadigmSpecialising in O Level Mathernatics5 In the diagram, ABC is a triangle where M is the midpoint of AC.The point P lies on the line BM such that BP=31BM.The point Q lies on the line BC such that BQ:QC=1:4.Given that AB=b and M0.(a) Express, as simply as possible, in terms of M1 and/or M2,(i) M3,(ii) M4,(iii) M5,(iv) M6.(b) Write down two facts about M7 and Q.(c) Find the numeral value of M9,Ans:(a)(i) AC0(ii) AC1(iii) AC2(iv) AC3(b) M7 and Q are collinear AC6(c) AC7
Vector BC Calculation: For BC, since M is the midpoint of AC, BC=BM+MC=BM+MA=BM−AM. Since AM=21AC, BC=BM−21AC. But BM=BA+AM=−AB+21AC=−b+21c. Therefore, BC=(−b+21c)−21c=−b.
Vector BM Calculation: For BM, since M is the midpoint of AC, BM=BA+AM=−AB+21AC=−b+21c.
Vector AP Calculation: For AP, since P divides BM in the ratio 1:2 (BP:PM=1:2), \vec{AP} = \vec{AB} + \vec{BP} = \vec{AB} + \frac{\(1\)}{\(3\)}\vec{BM} = \mathbf{b} + \frac{\(1\)}{\(3\)}(-\mathbf{b} + \frac{\(1\)}{\(2\)}\mathbf{c}) = \mathbf{b} - \frac{\(1\)}{\(3\)}\mathbf{b} + \frac{\(1\)}{\(6\)}\mathbf{c} = \frac{\(2\)}{\(3\)}\mathbf{b} + \frac{\(1\)}{\(6\)}\mathbf{c}.
Vector AQ Calculation: For \(\vec{AQ}\), since \(Q\) divides \(BC\) in the ratio \(1:4\) (\(BQ:QC = 1:4\)), \vec{AQ} = \vec{AB} + \vec{BQ} = \vec{AB} + \left(\frac{1}{5}\right)\vec{BC} = b + \left(\frac{1}{5}\right)(-b) = b - \left(\frac{1}{5}\right)b = \left(\frac{4}{5}\right)b.
Collinearity of Points: For part (b), since P lies on BM and Q lies on BC, and M is the midpoint of AC, it follows that A, P, and Q are collinear. Also, since AP:AQ=BP:BQ=1:4, BM0.
Area Ratio Calculation: For part (c), to find the area ratio, we use the fact that the areas of triangles with the same height are proportional to their bases. The area of triangle ABP is proportional to BP, and the area of quadrilateral CMPQ is the sum of the areas of triangles CMB and CMQ, which are proportional to BM and MQ, respectively. Since BP=31BM and MQ=54BC, and BC=2BM, BP0. The total base for the quadrilateral is BP1. Therefore, the area ratio is BP2. But we made a mistake, we forgot to consider the triangle CMB in the area of the quadrilateral, which should be added to MQ to get the total base. So, the correct total base for the quadrilateral is BP5. Therefore, the correct area ratio is BP6. But we made another mistake, the correct ratio of BP to the total base of the quadrilateral is BP8. This is the correct area ratio.
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