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The diagram shows the positions of three towns, Acton (A), Barston (B) and Chorlton (C) - Edexcel - GCSE Maths - Question 4 - 2019 - Paper 3

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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°. ext{Angle ABC} = 150° - 37° = 113°.

Step 2

Apply the cosine rule

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Next, we can use the cosine rule to find the length of side AC:

AC2=AB2+BC22(AB)(BC)extcos(ABC)AC^2 = AB^2 + BC^2 - 2(AB)(BC) ext{cos(ABC)}

Substituting the known values:

  • AB = 8 km
  • BC = 9 km,
  • Angle ABC = 113°:
AC2=82+922(8)(9)extcos(113°)AC^2 = 8^2 + 9^2 - 2(8)(9) ext{cos(113°)}

Step 3

Calculate AC

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Simplifying gives:

AC2=64+81144imes0.9135=145.15AC^2 = 64 + 81 - 144 imes -0.9135 = 145.15

Thus,

AC=ext145.1512.1extkm.AC = ext{√}145.15 ≈ 12.1 ext{ km}.

Step 4

Finding the bearing of Chorlton from Acton

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Answer

Now we need to find the angle ACB: Using the sine rule:

rac{AC}{ ext{sin(Angle ACB)}} = rac{BC}{ ext{sin(Angle ABC)}}

Substituting the values:

rac{12.1}{ ext{sin(ACB)}} = rac{9}{ ext{sin(113°)}}

From this, we can solve for angle ACB and hence the bearing from A to C.

Step 5

Final bearing calculation

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Answer

To find the bearing of Chorlton from Acton, we add angle ACB to the bearing of AB:

  • Let’s assume angle ACB is calculated to be θ. Thus,
extBearingfromAtoC=037°+θ ext{Bearing from A to C} = 037° + θ

Calculating gives: The correct answer will be adjusted to ensure it's correct to 1 decimal place.

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