Two fire look out stations are 20 miles apart with station B east of station A. Both station spot a fire?

Posted by admin on March 2nd, 2010 and filed under fire station | 3 Comments »

The bearing of the fire from station A is N 60 degrees east. The bearing of the fire from station B is North 40 degreese west. How far is it from station a to the the fire?

N 60° E means "60° east of north"
N 40° W means "40° west of north"

It helps if you draw a triangle.

If you draw vertical lines on either side of the triangle, you can see that the exterior angle of A is 60 degrees, so the inner angle must be 30.

The exterior angle of angle B is 40, so the inner angle is 50 degrees.

All the interior angles add up to 180 degrees, so angle C is 100 degrees.

A = 30 degrees
B= 50 degrees
C = 100 degrees
a = ?
b = ?
c = 20 miles

Now you can use the Rule of Sines to solve the rest.

a/sinA = b/sinB = c/sinC

b/sinB = 20/sin100

b = (20sin50)/sin100

b is about 15.57 miles

Using the same rule, a was about 10.2 miles.

Anyway the answer was 15.57 miles rounded up to 16.

3 Responses

  1. Rik D Says:

    N 60° E means "60° east of north"
    N 40° W means "40° west of north"

    d = sqrt( f^2 + h^2 )

    tan 30° = h/f =>

    f = h / tan 30°

    tan 50° = h / g =>

    g = h / tan 50°

    f + g = [h / tan 30°] + [h / tan 50°] = 20 =>

    (1 / tan 30° + 1 / tan 50° )h = 20 =>

    h = 20 / (1 / tan 30° + 1 / tan 50° )

    = 7.77861913 mi =>

    f = 7.77861913 / tan 30°

    = 13.4729635 mi =>

    d = sqrt( 13.4729635^2 + 7.77861913^2 )

    = 15.5572382 mi

    ˜ 15.6 mi
    References :
    Googled it

  2. Dilon Says:

    15.6 m
    References :

  3. Kim Says:

    N 60° E means "60° east of north"
    N 40° W means "40° west of north"

    It helps if you draw a triangle.

    If you draw vertical lines on either side of the triangle, you can see that the exterior angle of A is 60 degrees, so the inner angle must be 30.

    The exterior angle of angle B is 40, so the inner angle is 50 degrees.

    All the interior angles add up to 180 degrees, so angle C is 100 degrees.

    A = 30 degrees
    B= 50 degrees
    C = 100 degrees
    a = ?
    b = ?
    c = 20 miles

    Now you can use the Rule of Sines to solve the rest.

    a/sinA = b/sinB = c/sinC

    b/sinB = 20/sin100

    b = (20sin50)/sin100

    b is about 15.57 miles

    Using the same rule, a was about 10.2 miles.

    Anyway the answer was 15.57 miles rounded up to 16.
    References :

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