Question 92606
Avg. speed of Edna = 4 kmph due East.
Distance traversed by Edna in 4 hours = 4 x 4 = 16 km due East.


Avg. speed of Nancy = 3 kmph due North.
Distance traversed by Nancy in 4 hours = 4 x 3 = 12 km due North.


So, after 4 hrs. the straight line distance between them is
{{{sqrt(16^2 + 12^2)}}} = 20 km