Answer:
Step-by-step explanation:
Let the starting point be B and the stopping be C as shown in the diagram below.
therefore, the angle at A will be (197-90)degree = 107degree
the angle at B is 45degree, since it is directly south west of C.
therefore the angle at C will be A+B+C=180 degree(sum angle of a triangle)
107+45+C=180
therefore, C=180-107-45=28degree
therefore, using sine rule gives;
sinA/a =sinC/c
sin107/a=sin28/4
0.9563/a=0.4695/4
0.9563/a=0.11736
therefore, a =0.9563/0.11736=8.148=8.1km(approx.)
