The diagram shows the positions of three towns, Acton (A), Barston (B) and Chorlton (C) - Edexcel - GCSE Maths - Question 4 - 2019 - Paper 3
Question 4
The diagram shows the positions of three towns, Acton (A), Barston (B) and Chorlton (C).
Barston is 8km from Acton on a bearing of 037°
Chorlton is 9km from Barston... show full transcript
Worked Solution & Example Answer:The diagram shows the positions of three towns, Acton (A), Barston (B) and Chorlton (C) - Edexcel - GCSE Maths - Question 4 - 2019 - Paper 3
Step 1
Find angle ABC
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Answer
To find the required bearing of Chorlton from Acton, we first need to determine angle ABC. Since we know the bearings:
From A to B is 037°.
From B to C is 150°.
The angle ABC can be calculated as follows:
extAngleABC=150°−37°=113°.
Step 2
Apply the cosine rule
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Answer
Next, we can use the cosine rule to find the length of side AC:
AC2=AB2+BC2−2(AB)(BC)extcos(ABC)
Substituting the known values:
AB = 8 km
BC = 9 km,
Angle ABC = 113°:
AC2=82+92−2(8)(9)extcos(113°)
Step 3
Calculate AC
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Simplifying gives:
AC2=64+81−144imes−0.9135=145.15
Thus,
AC=ext√145.15≈12.1extkm.
Step 4
Finding the bearing of Chorlton from Acton
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Now we need to find the angle ACB:
Using the sine rule: