Question

A woman and her dog are out for a morning run to the river, which is located 4.0 KM away. The woman runs at 2.5 M/S in a straight line. The dog unleashed and runs back-and-forth at 4.5 M/S between his owner and the river, until she reaches the river. What is the total distance run by the dog?

Answer 1

River shore is located at distance

$d = 4 km$

speed of the woman is given as

$v_1 = 2.5 m/s$

now the time taken by the woman to cover the distance is

$t = \frac{d}{v}$

$t = \frac{4000}{2.5} = 1600 s$

for the same time interval the dog will run to and fro with speed 4.5 m/s

so the total distance moved by the dog is given by

$d = v* t$

$d = 4.5 * 1600$

$d = 7200 m$

so the total distance that dog will move is 7200 m or 7.2 km