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Bearings and scale drawingIB MYP Maths Extended: Flashcards

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How is a bearing measured?

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How is a bearing measured?
Clockwise from north, using three figures.
Write 45∘45^\circ as a bearing.
045∘045^\circ
What bearing is due east? due south? due west?
090∘090^\circ, 180∘180^\circ, 270∘270^\circ
What bearing is due north?
000∘000^\circ (three figures; 360∘360^\circ is not used)
How do you find a back bearing?
Add 180∘180^\circ if the bearing is less than 180∘180^\circ; subtract 180∘180^\circ if it is 180∘180^\circ or more.
Bearing of BB from AA is 130∘130^\circ. Bearing of AA from BB?
130∘+180∘=310∘130^\circ+180^\circ=310^\circ
Bearing of BB from AA is 250∘250^\circ. Bearing of AA from BB?
250∘−180∘=070∘250^\circ-180^\circ=070^\circ
What does a scale of 1:50 0001:50\,000 mean?
11 cm on the map is 50 00050\,000 cm (0.50.5 km) in real life.
How do you change a map distance to a real distance?
Multiply by the scale number, then convert the units.
How do you change a real distance to a map distance?
Change to the same units, then divide by the scale number.
A map has scale 1:25 0001:25\,000 and two towns are 88 cm apart. Real distance?
8×25 000=200 0008\times25\,000=200\,000 cm =2=2 km
Why do bearing problems often involve right-angled triangles?
North, east, south and west lines are at 90∘90^\circ to each other.
Which tools do you use to solve bearing problems?
Pythagoras, SOH CAH TOA and back bearings, with a sketch and north lines.
What should a scale drawing include?
A scale, a north line at each turn, bearings measured clockwise, and distances drawn to scale.

Exam questions on Bearings and scale drawing

  1. A ship sails from port AA to port BB on a bearing of 072∘072^\circ. Port CC is on a bearing of 162∘162^\circ from BB.
    Find the size of angle ABCABC.2 marks
  2. A map of an island has a scale of 1:50 0001:50\,000. The villages Karu and Mele are 6.46.4 cm apart on the map.
    Another map of the island has a scale of 1:25 0001:25\,000. Find the distance between Karu and Mele on this map.2 marks
  3. A walker leaves a hut HH and walks 88 km on a bearing of 040∘040^\circ to a lake LL. She then walks 66 km on a bearing of 130∘130^\circ to a summit SS.
    Show that angle HLSHLS is 90∘90^\circ and hence find the straight-line distance HSHS.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).