Kiley went 5.7 km/h north and then went 5.8 km/h west. from start to finish, she went 8.1 km/h northwest.

which best describes her numbers?
5.7 km/h north and 5.8 km/h west are instantaneous speeds, while 8.1 km/h northwest is the average speed.
5.7 km/h north and 5.8 km/h west are average speeds, while 8.1 km/h northwest is the instantaneous speed.
5.7 km/h north and 5.8 km/h west are average velocities, while 8.1 km/h northwest is the instantaneous velocity.
5.7 km/h north and 5.8 km/h west are instantaneous velocities,

5.7 km/h north and 5.8 km/h west are instantaneous velocities, 8.1 km/h northwest is the average velocity.

Velocity is a vector quantity while speed is a scalar quantity. A vector quantity has both magnitude and direction. The direction of the vector must be taken into account in vector calculations.

We can see that at the two instants mentioned, the instantaneous velocities of the body were 5.7 km/h north and then went 5.8 km/h west. The average velocity must be obtained bearing in mind the direction of the two velocities hence 8.1 km/h northwest is the average velocity obtained from Pythagoras theorem as follows;

Vav= √(5.7)^2 + (5.8)^2 =  8.1 km/h

Learn more: link

b) 10 minutes

girls stopped for 10 minutes.